diff --git a/constraints.go b/constraints.go
index c94fbc9..2daee9a 100644
--- a/constraints.go
+++ b/constraints.go
@@ -180,8 +180,13 @@ func init() {
 		ops,
 		cvRegex))
 
+	// The first time a constraint shows up will look slightly different from
+	// future times it shows up due to a leading space or comma in a given
+	// string.
 	validConstraintRegex = regexp.MustCompile(fmt.Sprintf(
-		`^(\s*(%s)\s*(%s)\s*\,?)+$`,
+		`^(\s*(%s)\s*(%s)\s*)((?:\s+|,\s*)(%s)\s*(%s)\s*)*$`,
+		ops,
+		cvRegex,
 		ops,
 		cvRegex))
 }
diff --git a/constraints_test.go b/constraints_test.go
index 477eb98..903cd8c 100644
--- a/constraints_test.go
+++ b/constraints_test.go
@@ -231,6 +231,15 @@ func TestNewConstraint(t *testing.T) {
 
 		// The 3 - 4 should be broken into 2 by the range rewriting
 		{"3 - 4 || => 3.0, < 4", 2, 2, false},
+
+		// Due to having 4 parts these should produce an error. See
+		// https://github.com/Masterminds/semver/issues/185 for the reason for
+		// these tests.
+		{"12.3.4.1234", 0, 0, true},
+		{"12.23.4.1234", 0, 0, true},
+		{"12.3.34.1234", 0, 0, true},
+		{"12.3.34 ~1.2.3", 1, 2, false},
+		{"12.3.34~ 1.2.3", 0, 0, true},
 	}
 
 	for _, tc := range tests {
diff --git a/version_test.go b/version_test.go
index a134d7a..b7289eb 100644
--- a/version_test.go
+++ b/version_test.go
@@ -87,6 +87,13 @@ func TestNewVersion(t *testing.T) {
 		{"1.2.2147483648", false},
 		{"1.2147483648.3", false},
 		{"2147483648.3.0", false},
+
+		// Due to having 4 parts these should produce an error. See
+		// https://github.com/Masterminds/semver/issues/185 for the reason for
+		// these tests.
+		{"12.3.4.1234", true},
+		{"12.23.4.1234", true},
+		{"12.3.34.1234", true},
 	}
 
 	for _, tc := range tests {