diff --git a/cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java b/cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java
index 370556583..b46c1cfca 100644
--- a/cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java
+++ b/cbor/src/main/java/com/fasterxml/jackson/dataformat/cbor/CBORParser.java
@@ -2886,7 +2886,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         if (len < 5) {
             int inPtr = _inputPtr;
             final byte[] inBuf = _inputBuffer;
-            int q = inBuf[inPtr] & 0xFF;
+            int q = _padQuadForNulls(inBuf[inPtr]);
             if (len > 1) {
                 q = (q << 8) + (inBuf[++inPtr] & 0xFF);
                 if (len > 2) {
@@ -2910,7 +2910,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         q1 = (q1 << 8) | (inBuf[inPtr++] & 0xFF);
         
         if (len < 9) {
-            int q2 = (inBuf[inPtr++] & 0xFF);
+            int q2 = _padQuadForNulls(inBuf[inPtr++]);
             int left = len - 5;
             if (left > 0) {
                 q2 = (q2 << 8) + (inBuf[inPtr++] & 0xFF);
@@ -2932,7 +2932,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         q2 =  (q2 << 8) | (inBuf[inPtr++] & 0xFF);
 
         if (len < 13) {
-            int q3 = (inBuf[inPtr++] & 0xFF);
+            int q3 = _padQuadForNulls(inBuf[inPtr++]);
             int left = len - 9;
             if (left > 0) {
                 q3 = (q3 << 8) + (inBuf[inPtr++] & 0xFF);
@@ -2981,7 +2981,7 @@ private final String _findDecodedLong(int len, int q1, int q2) throws IOExceptio
         } while ((len -= 4) > 3);
         // and then leftovers
         if (len > 0) {
-            int q = inBuf[inPtr] & 0xFF;
+            int q = _padQuadForNulls(inBuf[inPtr]);
             if (len > 1) {
                 q = (q << 8) + (inBuf[++inPtr] & 0xFF);
                 if (len > 2) {
@@ -3012,12 +3012,9 @@ private static int[] _growArrayTo(int[] arr, int minSize) {
     }
 
     // Helper method needed to fix [dataformats-binary#312], masking of 0x00 character
-    // 26-Feb-2022, tatu: not yet used
-    /*
-    private final static int _padLastQuad(int q, int bytes) {
-        return (bytes == 4) ? q : (q | (-1 << (bytes << 3)));
+    private final static int _padQuadForNulls(int firstByte) {
+        return (firstByte & 0xFF) | 0xFFFFFF00;
     }
-    */
 
     /*
     /**********************************************************
diff --git a/cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/failing/SymbolTable312Test.java b/cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/parse/SymbolTable312Test.java
similarity index 98%
rename from cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/failing/SymbolTable312Test.java
rename to cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/parse/SymbolTable312Test.java
index 8d88817fb..680f0d78b 100644
--- a/cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/failing/SymbolTable312Test.java
+++ b/cbor/src/test/java/com/fasterxml/jackson/dataformat/cbor/parse/SymbolTable312Test.java
@@ -1,4 +1,4 @@
-package com.fasterxml.jackson.dataformat.cbor.failing;
+package com.fasterxml.jackson.dataformat.cbor.parse;
 
 import java.nio.charset.StandardCharsets;
 
diff --git a/release-notes/CREDITS-2.x b/release-notes/CREDITS-2.x
index 491407d79..6a9eca605 100644
--- a/release-notes/CREDITS-2.x
+++ b/release-notes/CREDITS-2.x
@@ -225,3 +225,8 @@ Martin Giannechini (MartinGian@github)
 * Contributed fix for #295: (ion) `jackson-dataformat-ion` does not handle null.struct
   deserialization correctly
  (2.13.0)
+
+David Turner (DaveCTurner@github)
+
+* Reported #312: (cbor, smile) Short NUL-only keys incorrectly detected as duplicates
+ (2.14.0)
diff --git a/release-notes/VERSION-2.x b/release-notes/VERSION-2.x
index 750de4abf..511ed1677 100644
--- a/release-notes/VERSION-2.x
+++ b/release-notes/VERSION-2.x
@@ -14,6 +14,8 @@ Modules:
 
 #301: (cbor, smile) Missing configuration methods for format-specific
   parser/generator features
+#312: (cbor, smile) Short NUL-only keys incorrectly detected as duplicates
+ (reported by David T)
 
 2.13.1 (19-Dec-2021)
 
diff --git a/smile/src/main/java/com/fasterxml/jackson/dataformat/smile/SmileParser.java b/smile/src/main/java/com/fasterxml/jackson/dataformat/smile/SmileParser.java
index 4e0da53ab..d1bca9537 100644
--- a/smile/src/main/java/com/fasterxml/jackson/dataformat/smile/SmileParser.java
+++ b/smile/src/main/java/com/fasterxml/jackson/dataformat/smile/SmileParser.java
@@ -1793,6 +1793,7 @@ private final String _handleLongFieldName() throws IOException
             if (quads >= _quadBuffer.length) {
                 _quadBuffer = _growArrayTo(_quadBuffer, _quadBuffer.length + 256);
             }
+            q = _padLastQuad(q, bytes);
             _quadBuffer[quads++] = q;
             byteLen += bytes;
         }
@@ -1825,7 +1826,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         if (len < 5) {
             int inPtr = _inputPtr;
             final byte[] inBuf = _inputBuffer;
-            int q = inBuf[inPtr] & 0xFF;
+            int q = _padQuadForNulls(inBuf[inPtr]);
             if (len > 1) {
                 q = (q << 8) + (inBuf[++inPtr] & 0xFF);
                 if (len > 2) {
@@ -1849,7 +1850,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         q1 =  (q1 << 8) | (inBuf[inPtr++] & 0xFF);
         
         if (len < 9) {
-            int q2 = (inBuf[inPtr++] & 0xFF);
+            int q2 = _padQuadForNulls(inBuf[inPtr++]);
             int left = len - 5;
             if (left > 0) {
                 q2 = (q2 << 8) + (inBuf[inPtr++] & 0xFF);
@@ -1871,7 +1872,7 @@ private final String _findDecodedFromSymbols(final int len) throws IOException
         q2 = (q2 << 8) | (inBuf[inPtr++] & 0xFF);
 
         if (len < 13) {
-            int q3 = (inBuf[inPtr++] & 0xFF);
+            int q3 = _padQuadForNulls(inBuf[inPtr++]);
             int left = len - 9;
             if (left > 0) {
                 q3 = (q3 << 8) + (inBuf[inPtr++] & 0xFF);
@@ -1920,7 +1921,7 @@ private final String _findDecodedFixed12(int len, int q1, int q2) throws IOExcep
         } while ((len -= 4) > 3);
         // and then leftovers
         if (len > 0) {
-            int q = inBuf[inPtr] & 0xFF;
+            int q = _padQuadForNulls(inBuf[inPtr]);
             if (len > 1) {
                 q = (q << 8) + (inBuf[++inPtr] & 0xFF);
                 if (len > 2) {
@@ -1940,13 +1941,15 @@ private static int[] _growArrayTo(int[] arr, int minSize) {
         return Arrays.copyOf(arr, size);
     }
 
-    // Helper method needed to fix [dataformats-binary#312], masking of 0x00 character
-    // 26-Feb-2022, tatu: not yet used
-    /*
+    // Helper methods needed to fix [dataformats-binary#312], masking of 0x00 character
+
     private final static int _padLastQuad(int q, int bytes) {
         return (bytes == 4) ? q : (q | (-1 << (bytes << 3)));
     }
-    */
+
+    private final static int _padQuadForNulls(int firstByte) {
+        return (firstByte & 0xFF) | 0xFFFFFF00;
+    }
 
     /*
     /**********************************************************
diff --git a/smile/src/test/java/com/fasterxml/jackson/dataformat/smile/failing/SymbolTable312Test.java b/smile/src/test/java/com/fasterxml/jackson/dataformat/smile/parse/SymbolTable312Test.java
similarity index 98%
rename from smile/src/test/java/com/fasterxml/jackson/dataformat/smile/failing/SymbolTable312Test.java
rename to smile/src/test/java/com/fasterxml/jackson/dataformat/smile/parse/SymbolTable312Test.java
index 710d76908..07f459289 100644
--- a/smile/src/test/java/com/fasterxml/jackson/dataformat/smile/failing/SymbolTable312Test.java
+++ b/smile/src/test/java/com/fasterxml/jackson/dataformat/smile/parse/SymbolTable312Test.java
@@ -1,4 +1,4 @@
-package com.fasterxml.jackson.dataformat.smile.failing;
+package com.fasterxml.jackson.dataformat.smile.parse;
 
 import java.nio.charset.StandardCharsets;