diff --git a/configure.ac b/configure.ac
index d8b53c7..2568da1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -32,6 +32,17 @@ LDFLAGS="$LDFLAGS $($OBJFW_CONFIG $OBJFW_CONFIG_FLAGS --ldflags)"
 FRAMEWORK_LIBS="$($OBJFW_CONFIG $OBJFW_CONFIG_FLAGS --framework-libs) $LIBS"
 LIBS="$($OBJFW_CONFIG $OBJFW_CONFIG_FLAGS --libs --rpath) $LIBS"
 
+AX_CHECK_COMPILER_FLAGS(-std=gnu11, [
+	OBJCFLAGS="$OBJCFLAGS -std=gnu11"
+], [
+	AX_CHECK_COMPILER_FLAGS(-std=gnu1x, [
+		OBJCFLAGS="$OBJCFLAGS -std=gnu1x"
+	], [
+		AX_CHECK_COMPILER_FLAGS(-std=gnu99,
+			[OBJCFLAGS="$OBJCFLAGS -std=gnu99"])
+	])
+])
+
 AX_CHECK_COMPILER_FLAGS(-Wdocumentation,
 	[OBJCFLAGS="$OBJCFLAGS -Wdocumentation"])
 
diff --git a/src/O3DEngine.m b/src/O3DEngine.m
index 06a1337..0197772 100644
--- a/src/O3DEngine.m
+++ b/src/O3DEngine.m
@@ -31,7 +31,8 @@
 	self = [super init];
 
 	@try {
-		_renderer = [[renderer alloc] initWithOptions: options];
+		_renderer = [(id <O3DRenderer>)[(Class)renderer alloc]
+		    initWithOptions: options];
 	} @catch (id e) {
 		[self release];
 		@throw e;
diff --git a/src/O3DGlide3Renderer.m b/src/O3DGlide3Renderer.m
index fb6101e..c6a20ca 100644
--- a/src/O3DGlide3Renderer.m
+++ b/src/O3DGlide3Renderer.m
@@ -293,7 +293,7 @@ floatToScreenRefresh(float refresh)
 	hWnd = (FxU32)_winAPIWindow.hWnd;
 #endif
 
-	if ((_context = grSstWinOpen(hWnd, screenRefresh, screenRefresh,
+	if ((_context = grSstWinOpen(hWnd, screenResolution, screenRefresh,
 	    GR_COLORFORMAT_RGBA, GR_ORIGIN_LOWER_LEFT, 2, 1)) == 0)
 		@throw [OFInitializationFailedException
 		    exceptionWithClass: self.class];
diff --git a/src/O3DRenderer.h b/src/O3DRenderer.h
index 87ccf4b..5de2758 100644
--- a/src/O3DRenderer.h
+++ b/src/O3DRenderer.h
@@ -23,7 +23,6 @@ typedef OFPair OF_GENERIC(OFValue *, OFNumber *) *O3DResolution;
 @property (readonly, nonatomic) OFArray OF_GENERIC(OFPair OF_GENERIC(OFValue *,
     OFNumber *) *) *availableResolutions;
 
-+ (instancetype)alloc;
 - (instancetype)initWithOptions:
     (nullable OFDictionary OF_GENERIC(OFString *, id) *)options;
 - (void)createWithResolution: (O3DResolution)resolution;