diff --git a/Source/CFBag.c b/Source/CFBag.c
index d94da9b6..12f8cd06 100644
--- a/Source/CFBag.c
+++ b/Source/CFBag.c
@@ -108,7 +108,7 @@ CFBagCreate (CFAllocatorRef allocator, const void **values, CFIndex numValues,
 {
   return (CFBagRef)GSHashTableCreate (allocator, _kCFBagTypeID,
     values, values, numValues,
-    (const GSHashTableKeyCallBacks*)callBacks, NULL);
+    (const GSHashTableKeyCallBacks*)callBacks, NULL, true);
 }
 
 CFBagRef
diff --git a/Source/CFDictionary.c b/Source/CFDictionary.c
index 0945e690..60b27421 100644
--- a/Source/CFDictionary.c
+++ b/Source/CFDictionary.c
@@ -119,7 +119,7 @@ CFDictionaryCreate (CFAllocatorRef allocator, const void **keys,
   return (CFDictionaryRef)GSHashTableCreate (allocator, _kCFDictionaryTypeID,
     keys, values, numValues,
     (const GSHashTableKeyCallBacks*)keyCallBacks,
-    (const GSHashTableValueCallBacks*)valueCallBacks);
+    (const GSHashTableValueCallBacks*)valueCallBacks, false);
 }
 
 CFDictionaryRef
diff --git a/Source/CFSet.c b/Source/CFSet.c
index cc748744..5d3ca672 100644
--- a/Source/CFSet.c
+++ b/Source/CFSet.c
@@ -108,7 +108,7 @@ CFSetCreate (CFAllocatorRef allocator, const void **values, CFIndex numValues,
   return (CFSetRef) GSHashTableCreate (allocator, _kCFSetTypeID,
                                        values, values, numValues,
                                        (const GSHashTableKeyCallBacks *)
-                                       callBacks, NULL);
+                                       callBacks, NULL, false);
 }
 
 CFSetRef
diff --git a/Source/GSHashTable.c b/Source/GSHashTable.c
index 6dc18026..baafefdb 100644
--- a/Source/GSHashTable.c
+++ b/Source/GSHashTable.c
@@ -268,7 +268,8 @@ GSHashTableRef
 GSHashTableCreate (CFAllocatorRef alloc, CFTypeID typeID,
                    const void **keys, const void **values, CFIndex numValues,
                    const GSHashTableKeyCallBacks * keyCallBacks,
-                   const GSHashTableValueCallBacks * valueCallBacks)
+                   const GSHashTableValueCallBacks * valueCallBacks,
+                   Boolean shouldCount)
 {
   CFIndex arraySize;
   CFIndex capacity;
@@ -290,6 +291,9 @@ GSHashTableCreate (CFAllocatorRef alloc, CFTypeID typeID,
 
       new->_capacity = capacity;
 
+      if (shouldCount)
+        GSHashTableSetShouldCount (new);
+
       if (keyCallBacks == NULL)
         keyCallBacks = &_kGSNullHashTableKeyCallBacks;
       if (valueCallBacks == NULL)
@@ -306,8 +310,12 @@ GSHashTableCreate (CFAllocatorRef alloc, CFTypeID typeID,
             {
               bucket = GSHashTableFindBucket (new, keys[idx],
                                               _kGSHashTableInsert);
-              GSHashTableAddKeyValuePair (new, bucket, keys[idx], values[idx]);
-              new->_count += 1;
+              if (shouldCount || bucket->count <= 0)
+                {
+                  GSHashTableAddKeyValuePair (new, bucket, keys[idx],
+                                              values[idx]);
+                  new->_count += 1;
+                }
             }
         }
     }
@@ -324,7 +332,8 @@ GSHashTableCreateCopy (CFAllocatorRef alloc, GSHashTableRef table)
   count = GSHashTableGetCount (table);
   new = GSHashTableCreate (alloc, CFGetTypeID (table), NULL, NULL,
                            count, &table->_keyCallBacks,
-                           &table->_valueCallBacks);
+                           &table->_valueCallBacks,
+                           GSHashTableShouldCount (table));
   if (new)
     {
       CFIndex idx;
diff --git a/Source/GSHashTable.h b/Source/GSHashTable.h
index a6fb0574..c40d2a03 100644
--- a/Source/GSHashTable.h
+++ b/Source/GSHashTable.h
@@ -92,7 +92,8 @@ GS_PRIVATE GSHashTableRef
 GSHashTableCreate (CFAllocatorRef alloc, CFTypeID typeID,
                    const void **keys, const void **values, CFIndex count,
                    const GSHashTableKeyCallBacks * keyCallBacks,
-                   const GSHashTableValueCallBacks * valueCallBacks);
+                   const GSHashTableValueCallBacks * valueCallBacks,
+                   Boolean shouldCount);
 
 GS_PRIVATE GSHashTableRef
 GSHashTableCreateCopy (CFAllocatorRef alloc, GSHashTableRef table);
diff --git a/Tests/CFDictionary/create_duplicates.m b/Tests/CFDictionary/create_duplicates.m
new file mode 100644
index 00000000..f5b3713e
--- /dev/null
+++ b/Tests/CFDictionary/create_duplicates.m
@@ -0,0 +1,27 @@
+#include "CoreFoundation/CFDictionary.h"
+#include "CoreFoundation/CFString.h"
+#include "../CFTesting.h"
+
+int main (void)
+{
+  const void *keys[2];
+  const void *values[2];
+  CFDictionaryRef dict;
+
+  keys[0] = CFSTR ("k");
+  keys[1] = CFSTR ("k");
+  values[0] = CFSTR ("v1");
+  values[1] = CFSTR ("v2");
+
+  dict = CFDictionaryCreate (NULL, keys, values, 2,
+                             &kCFCopyStringDictionaryKeyCallBacks,
+                             &kCFTypeDictionaryValueCallBacks);
+  PASS_CF(CFDictionaryGetCount (dict) == 1,
+    "A key repeated in the input array is stored once.");
+  PASS_CF(CFDictionaryContainsKey (dict, CFSTR ("k")),
+    "The key is present.");
+
+  CFRelease (dict);
+
+  return 0;
+}
diff --git a/Tests/CFSet/create_duplicates.m b/Tests/CFSet/create_duplicates.m
new file mode 100644
index 00000000..afbea63c
--- /dev/null
+++ b/Tests/CFSet/create_duplicates.m
@@ -0,0 +1,24 @@
+#include "CoreFoundation/CFSet.h"
+#include "CoreFoundation/CFString.h"
+#include "../CFTesting.h"
+
+int main (void)
+{
+  const void *values[3];
+  CFSetRef set;
+
+  values[0] = CFSTR ("a");
+  values[1] = CFSTR ("b");
+  values[2] = CFSTR ("a");
+
+  set = CFSetCreate (NULL, values, 3, &kCFTypeSetCallBacks);
+  PASS_CF(CFSetGetCount (set) == 2,
+    "A value repeated in the input array is stored once.");
+  PASS_CF(CFSetContainsValue (set, CFSTR ("a"))
+    && CFSetContainsValue (set, CFSTR ("b")),
+    "Both distinct values are present.");
+
+  CFRelease (set);
+
+  return 0;
+}