Index: src/platform/posix/OFProcess.m
==================================================================
--- src/platform/posix/OFProcess.m
+++ src/platform/posix/OFProcess.m
@@ -129,10 +129,13 @@
 	@try {
 		void *pool = objc_autoreleasePoolPush();
 		const char *path;
 		char **argv;
 
+		_pid = -1;
+		_readPipe[0] = _writePipe[1] = -1;
+
 		if (pipe(_readPipe) != 0 || pipe(_writePipe) != 0)
 			@throw [OFInitializationFailedException
 			    exceptionWithClass: self.class];
 
 		path = [program cStringWithEncoding: [OFLocale encoding]];

Index: src/platform/windows/OFProcess.m
==================================================================
--- src/platform/windows/OFProcess.m
+++ src/platform/windows/OFProcess.m
@@ -117,10 +117,13 @@
 		void *pool;
 		OFMutableString *argumentsString;
 		of_char16_t *argumentsCopy;
 		size_t length;
 
+		_process = INVALID_HANDLE_VALUE;
+		_readPipe[0] = _writePipe[1] = NULL;
+
 		sa.nLength = sizeof(sa);
 		sa.bInheritHandle = TRUE;
 		sa.lpSecurityDescriptor = NULL;
 
 		if (!CreatePipe(&_readPipe[0], &_readPipe[1], &sa, 0))