Index: src/OFKeyValueCoding.h
==================================================================
--- src/OFKeyValueCoding.h
+++ src/OFKeyValueCoding.h
@@ -66,8 +66,18 @@
  * @param value The value for the specified undefined key
  * @param key The undefined key of the value to set
  */
 -  (void)setValue: (nullable id)value
   forUndefinedKey: (OFString*)key;
+
+/*!
+ * @brief This is called by @ref setValue:forKey: if the specified key is a
+ *	  scalar, but the value specified is `nil`.
+ *
+ * By default, this throws an @ref OFInvalidArgumentException.
+ *
+ * @param key The key for which the value `nil` was specified
+ */
+- (void)setNilValueForKey: (OFString*)key;
 @end
 
 OF_ASSUME_NONNULL_END

Index: src/OFObject+KeyValueCoding.m
==================================================================
--- src/OFObject+KeyValueCoding.m
+++ src/OFObject+KeyValueCoding.m
@@ -22,10 +22,11 @@
 #import "OFObject.h"
 #import "OFObject+KeyValueCoding.h"
 #import "OFString.h"
 #import "OFNumber.h"
 
+#import "OFInvalidArgumentException.h"
 #import "OFOutOfMemoryException.h"
 #import "OFUndefinedKeyException.h"
 
 int _OFObject_KeyValueCoding_reference;
 
@@ -137,10 +138,15 @@
 	if (*typeEncoding != 0) {
 		[self    setValue: value
 		  forUndefinedKey: key];
 		return;
 	}
+
+	if (valueType != '@' && valueType != '#' && value == nil) {
+		[self setNilValueForKey: key];
+		return;
+	}
 
 	switch (valueType) {
 	case '@':
 	case '#':
 		{
@@ -184,6 +190,11 @@
 {
 	@throw [OFUndefinedKeyException exceptionWithObject: self
 							key: key
 						      value: value];
 }
+
+- (void)setNilValueForKey: (OFString*)key
+{
+	@throw [OFInvalidArgumentException exception];
+}
 @end

Index: tests/OFObjectTests.m
==================================================================
--- tests/OFObjectTests.m
+++ tests/OFObjectTests.m
@@ -18,10 +18,11 @@
 
 #import "OFString.h"
 #import "OFNumber.h"
 #import "OFAutoreleasePool.h"
 
+#import "OFInvalidArgumentException.h"
 #import "OFMemoryNotPartOfObjectException.h"
 #import "OFOutOfMemoryException.h"
 #import "OFUndefinedKeyException.h"
 
 #import "TestsAppDelegate.h"
@@ -252,9 +253,13 @@
 	    [m unsignedIntValue] == 80 &&
 	    [m unsignedLongValue] == 90 &&
 	    [m unsignedLongLongValue] == 100 &&
 	    [m floatValue] == 110 &&
 	    [m doubleValue] == 120)
+
+	EXPECT_EXCEPTION(@"Catch -[setValue:forKey:] with nil key for scalar",
+	    OFInvalidArgumentException, [m setValue: nil
+					     forKey: @"intValue"])
 
 	[pool drain];
 }
 @end