diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fc23fcb4a40..58945f19b20 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2011-08-08  Richard Henderson  <rth@redhat.com>
+
+	PR middle-end/49990
+	* config/i386/i386.c (ix86_expand_prologue): Call
+	for SEH target gen_prologue_use instead of gen_blockage
+	at prologue's end.
+
 2011-08-08  Martin Jambor  <mjambor@suse.cz>
 
 	PR middle-end/49923
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index b50b3d018bb..9a21e6bf918 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10242,9 +10242,11 @@ ix86_expand_prologue (void)
     emit_insn (gen_cld ());
 
   /* SEH requires that the prologue end within 256 bytes of the start of
-     the function.  Prevent instruction schedules that would extend that.  */
+     the function.  Prevent instruction schedules that would extend that.
+     Further, prevent alloca modifications to the stack pointer from being
+     combined with prologue modifications.  */
   if (TARGET_SEH)
-    emit_insn (gen_blockage ());
+    emit_insn (gen_prologue_use (stack_pointer_rtx));
 }
 
 /* Emit code to restore REG using a POP insn.  */