diff --git a/cli/compose/template/template.go b/cli/compose/template/template.go
index 2792a09ba5..086194b8fe 100644
--- a/cli/compose/template/template.go
+++ b/cli/compose/template/template.go
@@ -7,7 +7,7 @@ import (
 )
 
 var delimiter = "\\$"
-var substitution = "[_a-z][_a-z0-9]*(?::?[-?][^}]+)?"
+var substitution = "[_a-z][_a-z0-9]*(?::?[-?][^}]*)?"
 
 var patternString = fmt.Sprintf(
 	"%s(?i:(?P<escaped>%s)|(?P<named>%s)|{(?P<braced>%s)}|(?P<invalid>))",
@@ -75,7 +75,9 @@ func Substitute(template string, mapping Mapping) (string, error) {
 			name, errorMessage := partition(substitution, ":?")
 			value, ok := mapping(name)
 			if !ok || value == "" {
-				err = &InvalidTemplateError{Template: errorMessage}
+				err = &InvalidTemplateError{
+					Template: fmt.Sprintf("required variable %s is missing a value: %s", name, errorMessage),
+				}
 				return ""
 			}
 			return value
@@ -84,7 +86,9 @@ func Substitute(template string, mapping Mapping) (string, error) {
 			name, errorMessage := partition(substitution, "?")
 			value, ok := mapping(name)
 			if !ok {
-				err = &InvalidTemplateError{Template: errorMessage}
+				err = &InvalidTemplateError{
+					Template: fmt.Sprintf("required variable %s is missing a value: %s", name, errorMessage),
+				}
 				return ""
 			}
 			return value
diff --git a/cli/compose/template/template_test.go b/cli/compose/template/template_test.go
index 66e50124ed..4fec57e8e8 100644
--- a/cli/compose/template/template_test.go
+++ b/cli/compose/template/template_test.go
@@ -97,23 +97,23 @@ func TestMandatoryVariableErrors(t *testing.T) {
 	}{
 		{
 			template:      "not ok ${UNSET_VAR:?Mandatory Variable Unset}",
-			expectedError: "Mandatory Variable Unset",
+			expectedError: "required variable UNSET_VAR is missing a value: Mandatory Variable Unset",
 		},
 		{
 			template:      "not ok ${BAR:?Mandatory Variable Empty}",
-			expectedError: "Mandatory Variable Empty",
+			expectedError: "required variable BAR is missing a value: Mandatory Variable Empty",
 		},
 		{
 			template:      "not ok ${UNSET_VAR:?}",
-			expectedError: "",
+			expectedError: "required variable UNSET_VAR is missing a value",
 		},
 		{
-			template:      "not ok ${UNSET_VAR?Mandatory Variable Unset",
-			expectedError: "Mandatory Variable Unset",
+			template:      "not ok ${UNSET_VAR?Mandatory Variable Unset}",
+			expectedError: "required variable UNSET_VAR is missing a value: Mandatory Variable Unset",
 		},
 		{
 			template:      "not ok ${UNSET_VAR?}",
-			expectedError: "",
+			expectedError: "required variable UNSET_VAR is missing a value",
 		},
 	}