diff --git a/tools/toolchains/arm.py b/tools/toolchains/arm.py
index f58a20b017..95d5930882 100644
--- a/tools/toolchains/arm.py
+++ b/tools/toolchains/arm.py
@@ -38,7 +38,7 @@ class ARM(mbedToolchain):
             "--brief_diagnostics", "--restrict", "--multibyte_chars", "-I \""+ARM_INC+"\""],
         'asm': [],
         'c': ["--md", "--no_depend_system_headers", "--c99", "-D__ASSERT_MSG"],
-        'cxx': ["--cpp", "--no_rtti"],
+        'cxx': ["--cpp", "--no_rtti", "--no_vla"],
         'ld': [],
     }
 
diff --git a/tools/toolchains/gcc.py b/tools/toolchains/gcc.py
index 3d0f9b5095..64f266a42d 100644
--- a/tools/toolchains/gcc.py
+++ b/tools/toolchains/gcc.py
@@ -38,7 +38,7 @@ class GCC(mbedToolchain):
             ],
         'asm': ["-x", "assembler-with-cpp"],
         'c': ["-std=gnu99"],
-        'cxx': ["-std=gnu++98", "-fno-rtti"],
+        'cxx': ["-std=gnu++98", "-fno-rtti", "-Wvla"],
         'ld': ["-Wl,--gc-sections", "-Wl,--wrap,main",
             "-Wl,--wrap,_malloc_r", "-Wl,--wrap,_free_r", "-Wl,--wrap,_realloc_r"],
     }