diff --git a/libguile/eval.c b/libguile/eval.c
index e7484376a..ed592af5e 100644
--- a/libguile/eval.c
+++ b/libguile/eval.c
@@ -2969,11 +2969,12 @@ scm_eval_body (SCM code, SCM env)
 	{
 	  if (SCM_ISYMP (SCM_CAR (code)))
 	    {
-	      scm_i_scm_pthread_mutex_lock (&source_mutex);
+	      scm_dynwind_begin (0);
+	      scm_dynwind_pthread_mutex_lock (&source_mutex);
 	      /* check for race condition */
 	      if (SCM_ISYMP (SCM_CAR (code)))
 		m_expand_body (code, env);
-	      scm_i_pthread_mutex_unlock (&source_mutex);
+	      scm_dynwind_end ();
 	      goto again;
 	    }
 	}
@@ -3367,11 +3368,12 @@ dispatch:
                 {
                   if (SCM_ISYMP (form))
                     {
-                      scm_i_scm_pthread_mutex_lock (&source_mutex);
+		      scm_dynwind_begin (0);
+		      scm_dynwind_pthread_mutex_lock (&source_mutex);
                       /* check for race condition */
                       if (SCM_ISYMP (SCM_CAR (x)))
                         m_expand_body (x, env);
-                      scm_i_pthread_mutex_unlock (&source_mutex);
+		      scm_dynwind_end ();
                       goto nontoplevel_begin;
                     }
                   else
@@ -4966,11 +4968,12 @@ tail:
 	    {
 	      if (SCM_ISYMP (SCM_CAR (proc)))
 		{
-		  scm_i_scm_pthread_mutex_lock (&source_mutex);
+		  scm_dynwind_begin (0);
+		  scm_dynwind_pthread_mutex_lock (&source_mutex);
 		  /* check for race condition */
 		  if (SCM_ISYMP (SCM_CAR (proc)))
 		    m_expand_body (proc, args);
-		  scm_i_pthread_mutex_unlock (&source_mutex);
+		  scm_dynwind_end ();
 		  goto again;
 		}
 	      else