diff --git a/terraform/eval_context_builtin.go b/terraform/eval_context_builtin.go
index f7a6829afe..61f35b7323 100644
--- a/terraform/eval_context_builtin.go
+++ b/terraform/eval_context_builtin.go
@@ -190,8 +190,15 @@ func (ctx *BuiltinEvalContext) ConfigureProvider(addr addrs.ProviderConfig, cfg
 		diags = diags.Append(fmt.Errorf("%s not initialized", addr))
 		return diags
 	}
+
+	providerSchema := ctx.ProviderSchema(absAddr)
+	if providerSchema == nil {
+		diags = diags.Append(fmt.Errorf("schema for %s is not available", absAddr))
+		return diags
+	}
+
 	// FIXME: The provider API isn't yet updated to take a cty.Value directly.
-	rc := NewResourceConfigShimmed(cfg, ctx.ProviderSchema(absAddr).Provider)
+	rc := NewResourceConfigShimmed(cfg, providerSchema.Provider)
 	err := p.Configure(rc)
 	if err != nil {
 		diags = diags.Append(err)
diff --git a/terraform/eval_validate.go b/terraform/eval_validate.go
index 7a35c23f4e..8a5e91fa7b 100644
--- a/terraform/eval_validate.go
+++ b/terraform/eval_validate.go
@@ -314,6 +314,10 @@ type EvalValidateResource struct {
 }
 
 func (n *EvalValidateResource) Eval(ctx EvalContext) (interface{}, error) {
+	if n.ProviderSchema == nil {
+		return nil, fmt.Errorf("EvalValidateResource has nil schema for %s", n.Addr)
+	}
+
 	var diags tfdiags.Diagnostics
 	provider := *n.Provider
 	cfg := *n.Config
diff --git a/terraform/transform_attach_schema.go b/terraform/transform_attach_schema.go
index 034af35d6c..4c51582299 100644
--- a/terraform/transform_attach_schema.go
+++ b/terraform/transform_attach_schema.go
@@ -104,11 +104,16 @@ func (t *AttachSchemaTransformer) Transform(g *Graph) error {
 			typeName := addr.Resource.Type
 			providerAddr, _ := tv.ProvidedBy()
 			var schema *configschema.Block
+			providerSchema := schemas[providerAddr.ProviderConfig.Type]
+			if providerSchema == nil {
+				log.Printf("[ERROR] AttachSchemaTransformer: No schema available for %s because provider schema for %q is missing", addr, providerAddr.ProviderConfig.Type)
+				continue
+			}
 			switch mode {
 			case addrs.ManagedResourceMode:
-				schema = schemas[providerAddr.ProviderConfig.Type].ResourceTypes[typeName]
+				schema = providerSchema.ResourceTypes[typeName]
 			case addrs.DataResourceMode:
-				schema = schemas[providerAddr.ProviderConfig.Type].DataSources[typeName]
+				schema = providerSchema.DataSources[typeName]
 			}
 			if schema != nil {
 				log.Printf("[TRACE] AttachSchemaTransformer: attaching schema to %s", dag.VertexName(v))
@@ -118,7 +123,14 @@ func (t *AttachSchemaTransformer) Transform(g *Graph) error {
 			}
 		case GraphNodeAttachProviderConfigSchema:
 			providerAddr := tv.ProviderAddr()
+			providerSchema := schemas[providerAddr.ProviderConfig.Type]
+			if providerSchema == nil {
+				log.Printf("[ERROR] AttachSchemaTransformer: No schema available for %s because the whole provider schema is missing", providerAddr)
+				continue
+			}
+
 			schema := schemas[providerAddr.ProviderConfig.Type].Provider
+
 			if schema != nil {
 				log.Printf("[TRACE] AttachSchemaTransformer: attaching schema to %s", dag.VertexName(v))
 				tv.AttachProviderConfigSchema(schema)