diff --git a/CHANGES.current b/CHANGES.current
index 5e9f9a866..f3976c5f4 100644
--- a/CHANGES.current
+++ b/CHANGES.current
@@ -5,6 +5,12 @@ See the RELEASENOTES file for a summary of changes in each release.
 Version 3.0.9 (in progress)
 ===========================
 
+2016-03-31: wsfulton
+	    [Java] unsigned long long marshalling improvements when a negative number
+            is passed from Java to C. A cast to signed long long in the C layer will now
+            result in the expected value. No change for positive numbers passed to C.
+            Fixes #623.
+
 2016-03-22: alexwarg
 	    [Lua] #398 Fix lua __getitem + inheritance
             The new handling of classes in Lua (not merging methods into the derived classes)
diff --git a/Examples/test-suite/java/long_long_runme.java b/Examples/test-suite/java/long_long_runme.java
index 3a967f7a7..76aa0705d 100644
--- a/Examples/test-suite/java/long_long_runme.java
+++ b/Examples/test-suite/java/long_long_runme.java
@@ -3,7 +3,8 @@
 // unsigned long long types map correctly to long and BigInteger respectively.
 
 import long_long.*;
-import java.math.*;
+import java.math.BigInteger;
+import java.util.ArrayList;
 
 public class long_long_runme {
 
@@ -54,12 +55,57 @@ public class long_long_runme {
       check_ull(testNumber);
       testNumber = testNumber.add(BigInteger.ONE);
     }
-    
+
     try {
       long_long.setUll(null);
       throw new RuntimeException("null check failed");
     } catch (NullPointerException e) {
     }
+
+    // UnsignedToSigned - checks that a cast from unsigned long long to long long in C
+    // gives expected value (including -ve numbers)
+
+    long[] nums = {
+       0x00,
+       0xFF,  0x80,  0x7F,  0x01,
+      -0xFF, -0x80, -0x7F, -0x01,
+       0x100,  0x10000,
+      -0x100, -0x10000,
+       0xFFFF,  0xFF80,  0xFF7F,  0xFF01,  0xFF00,
+      -0xFFFF, -0xFF80, -0xFF7F, -0xFF01, -0xFF00,
+       0x7FFF,  0x7F80,  0x7F7F,  0x7F01,  0x7F00,
+      -0x7FFF, -0x7F80, -0x7F7F, -0x7F01, -0x7F00,
+       0x80FF,  0x8080,  0x807F,  0x8001,  0x8000,
+      -0x80FF, -0x8080, -0x807F, -0x8001, -0x8000,
+      Integer.MAX_VALUE, Integer.MIN_VALUE,
+      Integer.MAX_VALUE+1, Integer.MIN_VALUE-1,
+      Long.MAX_VALUE, Long.MIN_VALUE,
+    };
+
+    ArrayList<BigInteger> bigIntegers = new ArrayList<BigInteger>();
+    for (int i=0; i<nums.length; ++i) {
+      BigInteger bi = new BigInteger(new Long(nums[i]).toString());
+      bigIntegers.add(bi);
+    }
+
+    {
+      BigInteger bi = new BigInteger(new Long(Long.MAX_VALUE).toString());
+      bigIntegers.add(bi.add(BigInteger.ONE));
+      bi = new BigInteger(new Long(Long.MIN_VALUE).toString());
+      bigIntegers.add(bi.subtract(BigInteger.ONE));
+    }
+
+    boolean failed = false;
+    for (int i=0; i<bigIntegers.size(); ++i) {
+      BigInteger bi = (BigInteger)bigIntegers.get(i);
+      long longReturn = long_long.UnsignedToSigned(bi);
+      if (bi.longValue() != longReturn) {
+        System.err.println("Conversion to long failed, in:" + bi + " out:" + longReturn);
+        failed = true;
+      }
+    }
+    if (failed)
+      throw new RuntimeException("There were UnsignedToSigned failures");
   }
 
   public static void check_ll(long ll) {
diff --git a/Examples/test-suite/long_long.i b/Examples/test-suite/long_long.i
index 74dd87a15..47acc15c6 100644
--- a/Examples/test-suite/long_long.i
+++ b/Examples/test-suite/long_long.i
@@ -38,3 +38,9 @@ unsigned long long ull;
 
 #define lconst5 987654321LL
 #define lconst6 987654321ULL
+
+%inline %{
+long long UnsignedToSigned(unsigned long long ull) {
+  return (long long)ull;
+}
+%}
diff --git a/Lib/java/java.swg b/Lib/java/java.swg
index f25a86605..96ca562b6 100644
--- a/Lib/java/java.swg
+++ b/Lib/java/java.swg
@@ -310,8 +310,11 @@ SWIGINTERN const char * SWIG_UnpackData(const char *c, void *ptr, size_t sz) {
   bae = JCALL2(GetByteArrayElements, jenv, ba, 0);
   sz = JCALL1(GetArrayLength, jenv, ba);
   $1 = 0;
-  for(i=0; i<sz; i++) {
-    $1 = ($1 << 8) | ($1_type)(unsigned char)bae[i];
+  if (sz > 0) {
+    $1 = ($1_type)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      $1 = ($1 << 8) | ($1_type)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
 }
@@ -334,8 +337,11 @@ SWIGINTERN const char * SWIG_UnpackData(const char *c, void *ptr, size_t sz) {
   bae = JCALL2(GetByteArrayElements, jenv, ba, 0);
   sz = JCALL1(GetArrayLength, jenv, ba);
   $result = 0;
-  for(i=0; i<sz; i++) {
-    $result = ($result << 8) | ($1_type)(unsigned char)bae[i];
+  if (sz > 0) {
+    $result = ($1_type)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      $result = ($result << 8) | ($1_type)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
 }
@@ -552,8 +558,11 @@ SWIGINTERN const char * SWIG_UnpackData(const char *c, void *ptr, size_t sz) {
   sz = JCALL1(GetArrayLength, jenv, ba);
   $1 = &temp;
   temp = 0;
-  for(i=0; i<sz; i++) {
-    temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+  if (sz > 0) {
+    temp = ($*1_ltype)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
 }
@@ -578,8 +587,11 @@ SWIGINTERN const char * SWIG_UnpackData(const char *c, void *ptr, size_t sz) {
   sz = JCALL1(GetArrayLength, jenv, ba);
   $result = &temp;
   temp = 0;
-  for(i=0; i<sz; i++) {
-    temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+  if (sz > 0) {
+    temp = ($*1_ltype)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
 }
diff --git a/Lib/java/typemaps.i b/Lib/java/typemaps.i
index e71790bcc..041cb24e0 100644
--- a/Lib/java/typemaps.i
+++ b/Lib/java/typemaps.i
@@ -109,8 +109,11 @@ INPUT_TYPEMAP(double, jdouble, double, "D");
   bae = JCALL2(GetByteArrayElements, jenv, ba, 0);
   sz = JCALL1(GetArrayLength, jenv, ba);
   temp = 0;
-  for(i=0; i<sz; i++) {
-    temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+  if (sz > 0) {
+    temp = ($*1_ltype)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
   $1 = &temp;
@@ -416,8 +419,11 @@ INOUT_TYPEMAP(double, jdouble, double, Double, "[Ljava/lang/Double;", jdoubleArr
   bae = JCALL2(GetByteArrayElements, jenv, ba, 0);
   sz = JCALL1(GetArrayLength, jenv, ba);
   temp = 0;
-  for(i=0; i<sz; i++) {
-    temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+  if (sz > 0) {
+    temp = ($*1_ltype)(signed char)bae[0];
+    for(i=1; i<sz; i++) {
+      temp = (temp << 8) | ($*1_ltype)(unsigned char)bae[i];
+    }
   }
   JCALL3(ReleaseByteArrayElements, jenv, ba, bae, 0);
   $1 = &temp;