diff --git a/libcpu/arm/cortex-m3/cpuport.c b/libcpu/arm/cortex-m3/cpuport.c
index 0a948c528b497e6a0e057cbb4202b7c5665cc468..d17d4fdf2e3c1d74239f509fd5fb86b53229646b 100644
--- a/libcpu/arm/cortex-m3/cpuport.c
+++ b/libcpu/arm/cortex-m3/cpuport.c
@@ -395,7 +395,6 @@ int __rt_ffs(int value)
         "ADDS    r0, r0, #0x01        \n"
 
         "exit:                        \n"
-        "BX      lr                   \n"
 
         : "=r"(value)
         : "r"(value)
diff --git a/libcpu/arm/cortex-m4/cpuport.c b/libcpu/arm/cortex-m4/cpuport.c
index 71a7fb16f9a7fa3a63c8f03d1341ad4367611a36..f556ba0c260413a08a58015175dfb4493933ebb9 100644
--- a/libcpu/arm/cortex-m4/cpuport.c
+++ b/libcpu/arm/cortex-m4/cpuport.c
@@ -479,7 +479,6 @@ int __rt_ffs(int value)
         "ADDS    r0, r0, #0x01        \n"
 
         "exit:                        \n"
-        "BX      lr                   \n"
 
         : "=r"(value)
         : "r"(value)
diff --git a/libcpu/arm/cortex-m7/cpuport.c b/libcpu/arm/cortex-m7/cpuport.c
index 85960baedecf687556a5db830c34a9666719c310..c22242f140e4b2751b538b4092f2cc4f1eaabe21 100644
--- a/libcpu/arm/cortex-m7/cpuport.c
+++ b/libcpu/arm/cortex-m7/cpuport.c
@@ -479,7 +479,6 @@ int __rt_ffs(int value)
         "ADDS    r0, r0, #0x01        \n"
 
         "exit:                        \n"
-        "BX      lr                   \n"
 
         : "=r"(value)
         : "r"(value)