diff --git a/command/format/diff.go b/command/format/diff.go
index 260c031de..c58661663 100644
--- a/command/format/diff.go
+++ b/command/format/diff.go
@@ -856,7 +856,7 @@ func ctyGetAttrMaybeNull(val cty.Value, name string) cty.Value {
 }
 
 func ctyCollectionValues(val cty.Value) []cty.Value {
-	if !val.IsKnown() {
+	if !val.IsKnown() || val.IsNull() {
 		return nil
 	}
 
diff --git a/helper/schema/resource.go b/helper/schema/resource.go
index 7d5a44aa7..a26dfc9f8 100644
--- a/helper/schema/resource.go
+++ b/helper/schema/resource.go
@@ -320,6 +320,11 @@ func (r *Resource) simpleDiff(
 		return instanceDiff, err
 	}
 
+	if instanceDiff == nil {
+		log.Printf("[DEBUG] Instance Diff is nil in SimpleDiff()")
+		return nil, err
+	}
+
 	// Make sure the old value is set in each of the instance diffs.
 	// This was done by the RequiresNew logic in the full legacy Diff.
 	for k, attr := range instanceDiff.Attributes {
@@ -331,14 +336,9 @@ func (r *Resource) simpleDiff(
 		}
 	}
 
-	if instanceDiff != nil {
-		if err := t.DiffEncode(instanceDiff); err != nil {
-			log.Printf("[ERR] Error encoding timeout to instance diff: %s", err)
-		}
-	} else {
-		log.Printf("[DEBUG] Instance Diff is nil in Diff()")
+	if err := t.DiffEncode(instanceDiff); err != nil {
+		log.Printf("[ERR] Error encoding timeout to instance diff: %s", err)
 	}
-
 	return instanceDiff, err
 }
 
diff --git a/plans/objchange/compatible.go b/plans/objchange/compatible.go
index 83b717554..8ac80ab05 100644
--- a/plans/objchange/compatible.go
+++ b/plans/objchange/compatible.go
@@ -64,7 +64,7 @@ func assertObjectCompatible(schema *configschema.Block, planned, actual cty.Valu
 				return errs
 			}
 		case configschema.NestingList, configschema.NestingMap, configschema.NestingSet:
-			if plannedV.IsKnown() && plannedV.LengthInt() == 1 {
+			if plannedV.IsKnown() && !plannedV.IsNull() && plannedV.LengthInt() == 1 {
 				elemVs := plannedV.AsValueSlice()
 				if allLeafValuesUnknown(elemVs[0]) {
 					return errs
@@ -84,7 +84,7 @@ func assertObjectCompatible(schema *configschema.Block, planned, actual cty.Valu
 			// whether there are dynamically-typed attributes inside. However,
 			// both support a similar-enough API that we can treat them the
 			// same for our purposes here.
-			if !plannedV.IsKnown() {
+			if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
 				continue
 			}
 
@@ -129,7 +129,7 @@ func assertObjectCompatible(schema *configschema.Block, planned, actual cty.Valu
 					}
 				}
 			} else {
-				if !plannedV.IsKnown() {
+				if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
 					continue
 				}
 				plannedL := plannedV.LengthInt()
@@ -153,7 +153,7 @@ func assertObjectCompatible(schema *configschema.Block, planned, actual cty.Valu
 			// content is also their key, and so we have no way to correlate
 			// them. Because of this, we simply verify that we still have the
 			// same number of elements.
-			if !plannedV.IsKnown() {
+			if !plannedV.IsKnown() || plannedV.IsNull() || actualV.IsNull() {
 				continue
 			}
 			plannedL := plannedV.LengthInt()
@@ -251,7 +251,7 @@ func assertValueCompatible(planned, actual cty.Value, path cty.Path) []error {
 		// so we can't correlate them properly. However, we will at least check
 		// to ensure that the number of elements is consistent, along with
 		// the general type-match checks we ran earlier in this function.
-		if planned.IsKnown() {
+		if planned.IsKnown() && !planned.IsNull() && !actual.IsNull() {
 			plannedL := planned.LengthInt()
 			actualL := actual.LengthInt()
 			if plannedL < actualL {
diff --git a/plans/objchange/objchange.go b/plans/objchange/objchange.go
index 5e68a780e..33e82dd52 100644
--- a/plans/objchange/objchange.go
+++ b/plans/objchange/objchange.go
@@ -92,8 +92,12 @@ func ProposedNewObject(schema *configschema.Block, prior, config cty.Value) cty.
 
 		case configschema.NestingList:
 			// Nested blocks are correlated by index.
-			if l := configV.LengthInt(); l > 0 {
-				newVals := make([]cty.Value, 0, l)
+			configVLen := 0
+			if configV.IsKnown() && !configV.IsNull() {
+				configVLen = configV.LengthInt()
+			}
+			if configVLen > 0 {
+				newVals := make([]cty.Value, 0, configVLen)
 				for it := configV.ElementIterator(); it.Next(); {
 					idx, configEV := it.Element()
 					if priorV.IsKnown() && (priorV.IsNull() || !priorV.HasIndex(idx).True()) {
@@ -130,8 +134,12 @@ func ProposedNewObject(schema *configschema.Block, prior, config cty.Value) cty.
 			// dynamically-typed attributes.
 			if configV.Type().IsObjectType() {
 				// Nested blocks are correlated by key.
-				if l := configV.LengthInt(); l > 0 {
-					newVals := make(map[string]cty.Value, l)
+				configVLen := 0
+				if configV.IsKnown() && !configV.IsNull() {
+					configVLen = configV.LengthInt()
+				}
+				if configVLen > 0 {
+					newVals := make(map[string]cty.Value, configVLen)
 					atys := configV.Type().AttributeTypes()
 					for name := range atys {
 						configEV := configV.GetAttr(name)
@@ -154,8 +162,12 @@ func ProposedNewObject(schema *configschema.Block, prior, config cty.Value) cty.
 					newV = cty.EmptyObjectVal
 				}
 			} else {
-				if l := configV.LengthInt(); l > 0 {
-					newVals := make(map[string]cty.Value, l)
+				configVLen := 0
+				if configV.IsKnown() && !configV.IsNull() {
+					configVLen = configV.LengthInt()
+				}
+				if configVLen > 0 {
+					newVals := make(map[string]cty.Value, configVLen)
 					for it := configV.ElementIterator(); it.Next(); {
 						idx, configEV := it.Element()
 						k := idx.AsString()
@@ -190,9 +202,13 @@ func ProposedNewObject(schema *configschema.Block, prior, config cty.Value) cty.
 			if priorV.IsKnown() && !priorV.IsNull() {
 				cmpVals = setElementCompareValues(&blockType.Block, priorV, false)
 			}
-			if l := configV.LengthInt(); l > 0 {
+			configVLen := 0
+			if configV.IsKnown() && !configV.IsNull() {
+				configVLen = configV.LengthInt()
+			}
+			if configVLen > 0 {
 				used := make([]bool, len(cmpVals)) // track used elements in case multiple have the same compare value
-				newVals := make([]cty.Value, 0, l)
+				newVals := make([]cty.Value, 0, configVLen)
 				for it := configV.ElementIterator(); it.Next(); {
 					_, configEV := it.Element()
 					var priorEV cty.Value