diff --git a/convex-core/src/test/java/convex/core/data/prim/BigIntegerTest.java b/convex-core/src/test/java/convex/core/data/prim/BigIntegerTest.java
index d416134f3..e99fa1dd5 100644
--- a/convex-core/src/test/java/convex/core/data/prim/BigIntegerTest.java
+++ b/convex-core/src/test/java/convex/core/data/prim/BigIntegerTest.java
@@ -97,14 +97,22 @@ public void testMaxSize() {
 		bs[0]=-128; // set sign bit for max sized negative number
 		ABlob blob=Blob.wrap(bs);
 		CVMBigInteger b=CVMBigInteger.create(blob);
+		
+		assertEquals(b,Samples.MIN_BIGINT);
+		
 		assertTrue(b.isCanonical());
 		assertEquals(Constants.MAX_BIG_INTEGER_LENGTH,b.blob().count());
+		
 		assertNull(b.negate());
 		assertNull(b.dec()); // overflow
 		assertNull(b.multiply(CVMLong.create(2))); // overflow
-		assertNotNull(b.inc().negate());
+		
+		// Negate to get maximum possible bigint
+		CVMBigInteger bn=(CVMBigInteger) b.inc().negate();
+		assertNotNull(bn);
 		
 		doBigTest(b);
+		doBigTest(bn);
 	}
 	
 	@Test 
@@ -163,7 +171,10 @@ public static void doBigTest(CVMBigInteger bi) {
 		assertEquals(bi.getEncoding(),bi2.getEncoding());
 		assertEquals(bi,bi2);
 		
-		assertEquals(bi,bi.inc().dec());
+		AInteger biplus=bi.inc();
+		if (biplus!=null) {
+			assertEquals(bi,biplus.dec());
+		}
 		
 		if (bi.isCanonical()) {
 			assertTrue(bi.byteLength()>8);
diff --git a/convex-core/src/test/java/convex/core/lang/CoreTest.java b/convex-core/src/test/java/convex/core/lang/CoreTest.java
index c1008ed87..8a07230c1 100644
--- a/convex-core/src/test/java/convex/core/lang/CoreTest.java
+++ b/convex-core/src/test/java/convex/core/lang/CoreTest.java
@@ -3295,7 +3295,12 @@ public void testQuot() {
 	@Test
 	public void testDiv() {
 		assertEquals(0L, evalL("(div 4 10)"));
+		assertEquals(0L, evalL("(div 0 -1)"));
 		assertEquals(-4L, evalL("(div -10 3)"));
+		
+		assertArgumentError(step("(div 3 0)"));
+		assertArgumentError(step("(div 0 0)"));
+		assertArgumentError(step("(div -1567567567567564756767586786785688 0)"));
 		// TODO: more tests
 	}
 
diff --git a/convex-core/src/test/java/convex/test/Samples.java b/convex-core/src/test/java/convex/test/Samples.java
index a09925d93..70eb7d27c 100644
--- a/convex-core/src/test/java/convex/test/Samples.java
+++ b/convex-core/src/test/java/convex/test/Samples.java
@@ -10,6 +10,7 @@
 import org.junit.jupiter.params.provider.Arguments;
 import org.junit.jupiter.params.provider.ArgumentsProvider;
 
+import convex.core.Constants;
 import convex.core.crypto.AKeyPair;
 import convex.core.crypto.ASignature;
 import convex.core.crypto.Ed25519Signature;
@@ -47,6 +48,7 @@
 import convex.core.data.VectorLeaf;
 import convex.core.data.VectorTree;
 import convex.core.data.Vectors;
+import convex.core.data.prim.CVMBigInteger;
 import convex.core.data.prim.CVMBool;
 import convex.core.data.prim.CVMChar;
 import convex.core.data.prim.CVMDouble;
@@ -156,12 +158,24 @@ public class Samples {
 
 	public static final Blob SMALL_BLOB = Blob.fromHex("cafebabe");
 	
+	public static final CVMBigInteger MAX_BIGINT;
+	public static final CVMBigInteger MIN_BIGINT;
+	
 	static {
 		// we should be able to actually build these, thanks to structural sharing.
 		DIABOLICAL_VECTOR_30_30 = createNastyNestedVector(30, 30);
 		DIABOLICAL_VECTOR_2_10000 = createNastyNestedVector(2, 10000);
 		DIABOLICAL_MAP_30_30 = createNastyNestedMap(30, 30);
 		DIABOLICAL_MAP_2_10000 = createNastyNestedMap(2, 10000);
+		 
+		{
+			byte [] bs=new byte[Constants.MAX_BIG_INTEGER_LENGTH];
+			bs[0]=-128; // set sign bit for max sized negative number
+			ABlob blob=Blob.wrap(bs);
+			CVMBigInteger b=CVMBigInteger.create(blob);
+			MIN_BIGINT=b;
+			MAX_BIGINT=(CVMBigInteger) b.inc().negate();
+		}
 	}
 	
 	/**