Index: src/runtime/OFOnce.m
==================================================================
--- src/runtime/OFOnce.m
+++ src/runtime/OFOnce.m
@@ -20,6 +20,11 @@
 #include "config.h"
 
 #import "ObjFWRT.h"
 #import "private.h"
 
+#import "OFOnce.h"
+
+extern void OFOnce(OFOnceControl *control, OFOnceFunction function)
+    OF_VISIBILITY_HIDDEN;
+
 #include "../OFOnce.m"

Index: src/runtime/OFPlainMutex.m
==================================================================
--- src/runtime/OFPlainMutex.m
+++ src/runtime/OFPlainMutex.m
@@ -20,6 +20,24 @@
 #include "config.h"
 
 #import "ObjFWRT.h"
 #import "private.h"
 
+#import "OFPlainMutex.h"
+
+extern int OFPlainMutexNew(OFPlainMutex *mutex) OF_VISIBILITY_HIDDEN;
+extern int OFPlainMutexLock(OFPlainMutex *mutex) OF_VISIBILITY_HIDDEN;
+extern int OFPlainMutexTryLock(OFPlainMutex *mutex) OF_VISIBILITY_HIDDEN;
+extern int OFPlainMutexUnlock(OFPlainMutex *mutex) OF_VISIBILITY_HIDDEN;
+extern int OFPlainMutexFree(OFPlainMutex *mutex) OF_VISIBILITY_HIDDEN;
+extern int OFPlainRecursiveMutexNew(OFPlainRecursiveMutex *rmutex)
+    OF_VISIBILITY_HIDDEN;
+extern int OFPlainRecursiveMutexLock(OFPlainRecursiveMutex *rmutex)
+    OF_VISIBILITY_HIDDEN;
+extern int OFPlainRecursiveMutexTryLock(OFPlainRecursiveMutex *rmutex)
+    OF_VISIBILITY_HIDDEN;
+extern int OFPlainRecursiveMutexUnlock(OFPlainRecursiveMutex *rmutex)
+    OF_VISIBILITY_HIDDEN;
+extern int OFPlainRecursiveMutexFree(OFPlainRecursiveMutex *rmutex)
+    OF_VISIBILITY_HIDDEN;
+
 #include "../OFPlainMutex.m"

Index: src/runtime/OFTLSKey.m
==================================================================
--- src/runtime/OFTLSKey.m
+++ src/runtime/OFTLSKey.m
@@ -20,6 +20,11 @@
 #include "config.h"
 
 #import "ObjFWRT.h"
 #import "private.h"
 
+#import "OFTLSKey.h"
+
+extern int OFTLSKeyNew(OFTLSKey *key) OF_VISIBILITY_HIDDEN;
+extern int OFTLSKeyFree(OFTLSKey key) OF_VISIBILITY_HIDDEN;
+
 #include "../OFTLSKey.m"