diff --git a/build.c b/build.c
index 42bc8f40..8668786c 100644
--- a/build.c
+++ b/build.c
@@ -73,27 +73,23 @@ struct StepList {
 
 void AddStep(String name, T_TaskFunc *func, void *arg)
 {
-    OS_MutexLockE(&sl->mutex);
-    {
-        Step *s = ArenaPush(&sl->arena, Step);
-        s->res_mutex = OS_MutexAlloc();
-        s->res_cv = OS_ConditionVariableAlloc();
-        s->name = name;
-        s->arg = arg;
-        SllQueuePush(sl->first, sl->last, s);
-        ++sl->count;
-        T_AddTask(&sl->tq, func, s);
-    }
-    OS_MutexUnlockE(&sl->mutex);
+    OS_Lock lock = OS_MutexLockE(&sl->mutex);
+    Step *s = ArenaPush(&sl->arena, Step);
+    s->res_mutex = OS_MutexAlloc();
+    s->res_cv = OS_ConditionVariableAlloc();
+    s->name = name;
+    s->arg = arg;
+    SllQueuePush(sl->first, sl->last, s);
+    ++sl->count;
+    T_AddTask(&sl->tq, func, s);
+    OS_MutexUnlock(&lock);
 }
 
 void AddSyncPoint(void)
 {
-    OS_MutexLockE(&sl->mutex);
-    {
-        T_AddSyncPoint(&sl->tq);
-    }
-    OS_MutexUnlockE(&sl->mutex);
+    OS_Lock lock = OS_MutexLockE(&sl->mutex);
+    T_AddSyncPoint(&sl->tq);
+    OS_MutexUnlock(&lock);
 }
 
 void ExecuteSteps(void)
@@ -126,21 +122,21 @@ void BuildStepSimpleCommand(void *arg_raw)
     BuildStepSimpleCommandArg *arg = s->arg;
     SH_CommandResult result = SH_RunCommandCaptureOutput(scratch.arena, arg->cmd, true);
 
-    OS_MutexLockE(&s->res_mutex);
     {
+        OS_Lock res_lock = OS_MutexLockE(&s->res_mutex);
         if (result.output.len > 0) {
-            OS_MutexLockE(&sl->mutex);
+            OS_Lock sl_lock = OS_MutexLockE(&sl->mutex);
             {
                 s->res_output.text = ArenaPushArrayNoZero(&sl->arena, Byte, result.output.len);
             }
-            OS_MutexUnlockE(&sl->mutex);
+            OS_MutexUnlock(&sl_lock);
             s->res_output.len = result.output.len;
             MemoryCopy(s->res_output.text, result.output.text, result.output.len);
         }
         s->res_status = result.error ? StepStatus_Failure : StepStatus_Success;
         OS_ConditionVariableBroadcast(&s->res_cv);
+        OS_MutexUnlock(&res_lock);
     }
-    OS_MutexUnlockE(&s->res_mutex);
 
     ScratchEnd(scratch);
 }
@@ -158,21 +154,21 @@ void BuildStepMsvcCompileCommand(void *arg_raw)
         D_ClearWrite(arg->output_depfile, depfile_data);
     }
 
-    OS_MutexLockE(&s->res_mutex);
     {
+        OS_Lock res_lock = OS_MutexLockE(&s->res_mutex);
         if (result.output.len > 0) {
-            OS_MutexLockE(&sl->mutex);
+            OS_Lock sl_lock = OS_MutexLockE(&sl->mutex);
             {
                 s->res_output.text = ArenaPushArrayNoZero(&sl->arena, Byte, result.output.len);
             }
-            OS_MutexUnlockE(&sl->mutex);
+            OS_MutexUnlock(&sl_lock);
             s->res_output.len = result.output.len;
             MemoryCopy(s->res_output.text, result.output.text, result.output.len);
         }
         s->res_status = result.error ? StepStatus_Failure : StepStatus_Success;
         OS_ConditionVariableBroadcast(&s->res_cv);
+        OS_MutexUnlock(&res_lock);
     }
-    OS_MutexUnlockE(&s->res_mutex);
 
     ScratchEnd(scratch);
 }
@@ -835,13 +831,13 @@ void OnBuild(StringList cli_args)
 
             SH_PrintF(Lit("[%F/%F] %F\n"), FmtI64(step_i), FmtI64(step_count), FmtStr(s->name));
 
-            OS_MutexLockS(&s->res_mutex);
             {
+                OS_Lock lock = OS_MutexLockS(&s->res_mutex);
                 while (s->res_status == StepStatus_None) {
-                    OS_ConditionVariableWaitS(&s->res_cv, &s->res_mutex);
+                    OS_ConditionVariableWait(&s->res_cv, &lock);
                 }
+                OS_MutexUnlock(&lock);
             }
-            OS_MutexUnlockS(&s->res_mutex);
 
             String output = s->res_output;
             if (s->res_status != StepStatus_Success) {