diff --git a/tools/toolchains/arm.py b/tools/toolchains/arm.py
index 09f76a8fa4..b609784e74 100644
--- a/tools/toolchains/arm.py
+++ b/tools/toolchains/arm.py
@@ -102,7 +102,7 @@ class ARM(mbedToolchain):
         stdout, _, retcode = run_cmd([self.cc[0], "--vsn"], redirect=True)
         msg = None
         min_ver, max_ver = self.ARMCC_RANGE
-        match = self.ARMCC_VERSION_RE.search(stdout)
+        match = self.ARMCC_VERSION_RE.search(stdout.encode("utf-8"))
         found_version = LooseVersion(match.group(1).decode("utf-8")) if match else None
         min_ver, max_ver = self.ARMCC_RANGE
         if found_version and (found_version < min_ver or found_version >= max_ver):
diff --git a/tools/toolchains/gcc.py b/tools/toolchains/gcc.py
index af3c5ca6aa..d2fd8cb258 100644
--- a/tools/toolchains/gcc.py
+++ b/tools/toolchains/gcc.py
@@ -133,7 +133,7 @@ class GCC(mbedToolchain):
     def version_check(self):
         stdout, _, retcode = run_cmd([self.cc[0], "--version"], redirect=True)
         msg = None
-        match = self.GCC_VERSION_RE.search(stdout)
+        match = self.GCC_VERSION_RE.search(stdout.encode("utf-8"))
         found_version = LooseVersion(match.group(0).decode('utf-8')) if match else None
         min_ver, max_ver = self.GCC_RANGE
         if found_version and (found_version < min_ver or found_version >= max_ver):
diff --git a/tools/toolchains/iar.py b/tools/toolchains/iar.py
index c94d5f089d..37c085295b 100644
--- a/tools/toolchains/iar.py
+++ b/tools/toolchains/iar.py
@@ -99,7 +99,7 @@ class IAR(mbedToolchain):
     def version_check(self):
         stdout, _, retcode = run_cmd([self.cc[0], "--version"], redirect=True)
         msg = None
-        match = self.IAR_VERSION_RE.search(stdout)
+        match = self.IAR_VERSION_RE.search(stdout.encode("utf-8"))
         found_version = match.group(1).decode("utf-8") if match else None
         if found_version and LooseVersion(found_version) != self.IAR_VERSION:
             msg = "Compiler version mismatch: Have {}; expected {}".format(