diff --git a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_ARM/TARGET_CORTEX_A/irq_ca.S b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_ARM/TARGET_CORTEX_A/irq_ca.S
index e916d8de22..033aff7c22 100644
--- a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_ARM/TARGET_CORTEX_A/irq_ca.S
+++ b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_ARM/TARGET_CORTEX_A/irq_ca.S
@@ -178,6 +178,11 @@ IRQ_Handler\
                 CPS     #MODE_SVC                   ; Change to SVC mode
                 PUSH    {R0-R3, R12, LR}            ; Save APCS corruptible registers
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                ADD     R2, R2, #1                  ; Increment IRQ nesting level
+                STR     R2, [R3]
+
                 MOV     R3, SP                      ; Move SP into R3
                 AND     R3, R3, #4                  ; Get stack adjustment to ensure 8-byte alignment
                 SUB     SP, SP, R3                  ; Adjust stack
@@ -186,11 +191,6 @@ IRQ_Handler\
                 BLX     IRQ_GetActiveIRQ            ; Retrieve interrupt ID into R0
                 MOV     R4, R0                      ; Move interrupt ID to R4
 
-                LDR     R1, =IRQ_NestLevel
-                LDR     R3, [R1]                    ; Load IRQ nest level and increment it
-                ADD     R3, R3, #1
-                STR     R3, [R1]
-
                 BLX     IRQ_GetHandler              ; Retrieve interrupt handler address for current ID
                 CMP     R0, #0                      ; Check if handler address is 0
                 BEQ     IRQ_End                     ; If 0, end interrupt and return
@@ -203,11 +203,10 @@ IRQ_End
                 MOV     R0, R4                      ; Move interrupt ID to R0
                 BLX     IRQ_EndOfInterrupt          ; Signal end of interrupt
 
-                LDR     R2, =IRQ_NestLevel
-                LDR     R1, [R2]                    ; Load IRQ nest level and
-                SUBS    R1, R1, #1                  ; decrement it
-                STR     R1, [R2]
-                BNE     IRQ_Exit                    ; Not zero, exit from IRQ handler
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]                    ; Load IRQ nest level
+                CMP     R2, #1
+                BNE     IRQ_Exit                    ; Nesting interrupts, exit from IRQ handler
 
                 LDR     R0, =SVC_Active
                 LDRB    R0, [R0]                    ; Load SVC_Active flag
@@ -252,12 +251,23 @@ IRQ_SwitchCheck
 
                 POP     {R3, R4}                    ; Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  ; Unadjust stack
+
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  ; Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 B       osRtxContextSwitch
 
 IRQ_Exit
                 POP     {R3, R4}                    ; Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  ; Unadjust stack
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  ; Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 POP     {R0-R3, R12, LR}            ; Restore stacked APCS registers
                 RFEFD   SP!                         ; Return from IRQ handler
 
diff --git a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_GCC/TARGET_CORTEX_A/irq_ca.S b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_GCC/TARGET_CORTEX_A/irq_ca.S
index b1c90cc321..99ad63a966 100644
--- a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_GCC/TARGET_CORTEX_A/irq_ca.S
+++ b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_GCC/TARGET_CORTEX_A/irq_ca.S
@@ -184,6 +184,11 @@ IRQ_Handler:
                 CPS     #MODE_SVC                   // Change to SVC mode
                 PUSH    {R0-R3, R12, LR}            // Save APCS corruptible registers
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                ADD     R2, R2, #1                  // Increment IRQ nesting level
+                STR     R2, [R3]
+
                 MOV     R3, SP                      // Move SP into R3
                 AND     R3, R3, #4                  // Get stack adjustment to ensure 8-byte alignment
                 SUB     SP, SP, R3                  // Adjust stack
@@ -192,11 +197,6 @@ IRQ_Handler:
                 BLX     IRQ_GetActiveIRQ            // Retrieve interrupt ID into R0
                 MOV     R4, R0                      // Move interrupt ID to R4
 
-                LDR     R1, =IRQ_NestLevel
-                LDR     R3, [R1]                    // Load IRQ nest level and increment it
-                ADD     R3, R3, #1
-                STR     R3, [R1]
-
                 BLX     IRQ_GetHandler              // Retrieve interrupt handler address for current ID
                 CMP     R0, #0                      // Check if handler address is 0
                 BEQ     IRQ_End                     // If 0, end interrupt and return
@@ -209,11 +209,10 @@ IRQ_End:
                 MOV     R0, R4                      // Move interrupt ID to R0
                 BLX     IRQ_EndOfInterrupt          // Signal end of interrupt
 
-                LDR     R2, =IRQ_NestLevel
-                LDR     R1, [R2]                    // Load IRQ nest level and
-                SUBS    R1, R1, #1                  // decrement it
-                STR     R1, [R2]
-                BNE     IRQ_Exit                    // Not zero, exit from IRQ handler
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]                    // Load IRQ nest level
+                CMP     R2, #1
+                BNE     IRQ_Exit                    // Nesting interrupts, exit from IRQ handler
 
                 LDR     R0, =SVC_Active
                 LDRB    R0, [R0]                    // Load SVC_Active flag
@@ -258,12 +257,23 @@ IRQ_SwitchCheck:
 
                 POP     {R3, R4}                    // Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  // Unadjust stack
+
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  // Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 B       osRtxContextSwitch
 
 IRQ_Exit:
                 POP     {R3, R4}                    // Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  // Unadjust stack
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  // Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 POP     {R0-R3, R12, LR}            // Restore stacked APCS registers
                 RFEFD   SP!                         // Return from IRQ handler
 
diff --git a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_IAR/TARGET_CORTEX_A/irq_ca.S b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_IAR/TARGET_CORTEX_A/irq_ca.S
index f3d0444ef8..3a66617e81 100644
--- a/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_IAR/TARGET_CORTEX_A/irq_ca.S
+++ b/rtos/TARGET_CORTEX/rtx5/RTX/Source/TOOLCHAIN_IAR/TARGET_CORTEX_A/irq_ca.S
@@ -169,6 +169,11 @@ IRQ_Handler
                 CPS     #MODE_SVC                   ; Change to SVC mode
                 PUSH    {R0-R3, R12, LR}            ; Save APCS corruptible registers
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                ADD     R2, R2, #1                  ; Increment IRQ nesting level
+                STR     R2, [R3]
+
                 MOV     R3, SP                      ; Move SP into R3
                 AND     R3, R3, #4                  ; Get stack adjustment to ensure 8-byte alignment
                 SUB     SP, SP, R3                  ; Adjust stack
@@ -177,11 +182,6 @@ IRQ_Handler
                 BLX     IRQ_GetActiveIRQ            ; Retrieve interrupt ID into R0
                 MOV     R4, R0                      ; Move interrupt ID to R4
 
-                LDR     R1, =IRQ_NestLevel
-                LDR     R3, [R1]                    ; Load IRQ nest level and increment it
-                ADD     R3, R3, #1
-                STR     R3, [R1]
-
                 BLX     IRQ_GetHandler              ; Retrieve interrupt handler address for current ID
                 CMP     R0, #0                      ; Check if handler address is 0
                 BEQ     IRQ_End                     ; If 0, end interrupt and return
@@ -194,11 +194,10 @@ IRQ_End
                 MOV     R0, R4                      ; Move interrupt ID to R0
                 BLX     IRQ_EndOfInterrupt          ; Signal end of interrupt
 
-                LDR     R2, =IRQ_NestLevel
-                LDR     R1, [R2]                    ; Load IRQ nest level and
-                SUBS    R1, R1, #1                  ; decrement it
-                STR     R1, [R2]
-                BNE     IRQ_Exit                    ; Not zero, exit from IRQ handler
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]                    ; Load IRQ nest level
+                CMP     R2, #1
+                BNE     IRQ_Exit                    ; Nesting interrupts, exit from IRQ handler
 
                 LDR     R0, =SVC_Active
                 LDRB    R0, [R0]                    ; Load SVC_Active flag
@@ -243,12 +242,23 @@ IRQ_SwitchCheck
 
                 POP     {R3, R4}                    ; Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  ; Unadjust stack
+
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  ; Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 B       osRtxContextSwitch
 
 IRQ_Exit
                 POP     {R3, R4}                    ; Restore stack adjustment(R3) and user data(R4)
                 ADD     SP, SP, R3                  ; Unadjust stack
 
+                LDR     R3, =IRQ_NestLevel
+                LDR     R2, [R3]
+                SUBS    R2, R2, #1                  ; Decrement IRQ nesting level
+                STR     R2, [R3]
+
                 POP     {R0-R3, R12, LR}            ; Restore stacked APCS registers
                 RFEFD   SP!                         ; Return from IRQ handler