diff --git a/cortex-m-rt/src/lib.rs b/cortex-m-rt/src/lib.rs
index 6f721975..c61c1e8e 100644
--- a/cortex-m-rt/src/lib.rs
+++ b/cortex-m-rt/src/lib.rs
@@ -573,10 +573,12 @@ cfg_global_asm! {
      isb",
 
     // Push `lr` to the stack for debuggers, to prevent them unwinding past Reset.
-    // See https://sourceware.org/binutils/docs/as/CFI-directives.html.
+    // Push a dummy `r4` (which is always 0xFFFF_FFFF) to ensure the stack stays 8-byte aligned.
+    // For CFI information, see https://sourceware.org/binutils/docs/as/CFI-directives.html.
+    // For 8 byte alignment, see https://github.com/ARM-software/abi-aa/blob/edd7460d87493fff124b8b5713acf71ffc06ee91/aapcs32/aapcs32.rst#6212stack-constraints-at-a-public-interface.
     ".cfi_def_cfa sp, 0
-     push {{lr}}
-     .cfi_offset lr, 0",
+     push {{r4, lr}}
+     .cfi_offset lr, 4",
 
     // Jump to user main function.
     // `bl` is used for the extended range, but the user main function should not return,