diff --git a/spdxexp/parse.go b/spdxexp/parse.go
index f66de71..17df0ab 100644
--- a/spdxexp/parse.go
+++ b/spdxexp/parse.go
@@ -99,6 +99,11 @@ func (t *tokenStream) parseParenthesizedExpression() *node {
 		// paren not found
 		return nil
 	}
+	if !t.hasMore() {
+		// catch the case where there are no tokens after an open parenthesis
+		t.err = errors.New("open parenthesis does not have a matching close parenthesis")
+		return nil
+	}
 
 	expr := t.parseExpression()
 	if t.err != nil {
@@ -106,13 +111,14 @@ func (t *tokenStream) parseParenthesizedExpression() *node {
 	}
 
 	if !t.hasMore() {
-		// no more tokens, so missing closing paren
+		// catch the case where there are no tokens after processing expression starting with an open parenthesis
 		t.err = errors.New("open parenthesis does not have a matching close parenthesis")
 		return nil
 	}
 
 	closeParen := t.parseOperator(")")
 	if closeParen == nil {
+		// catch the case where the next token is not the expected close parenthesis
 		t.err = errors.New("open parenthesis does not have a matching close parenthesis")
 		return nil
 	}
@@ -281,6 +287,9 @@ func (t *tokenStream) parseLicenseRef() *node {
 	ref := referenceNodePartial{documentRef: "", hasDocumentRef: false, licenseRef: ""}
 
 	token := t.peek()
+	if token == nil {
+		return nil
+	}
 	if token.role == documentRefToken {
 		ref.documentRef = token.value
 		ref.hasDocumentRef = true
@@ -294,6 +303,12 @@ func (t *tokenStream) parseLicenseRef() *node {
 	}
 
 	token = t.peek()
+	if token == nil {
+		if ref.hasDocumentRef {
+			t.err = errors.New("expected 'LicenseRef-...' after 'DocumentRef-...'")
+		}
+		return nil
+	}
 	if token.role != licenseRefToken && ref.hasDocumentRef {
 		t.err = errors.New("expected 'LicenseRef-...' after 'DocumentRef-...'")
 		return nil
@@ -315,6 +330,9 @@ func (t *tokenStream) parseLicenseRef() *node {
 // an error is returned.  Advances the index if a valid license is found.
 func (t *tokenStream) parseLicense() *node {
 	token := t.peek()
+	if token == nil {
+		return nil
+	}
 	if token.role != licenseToken {
 		return nil
 	}
@@ -361,6 +379,9 @@ func (t *tokenStream) parseLicense() *node {
 // Advances the index if the operator is found.
 func (t *tokenStream) parseOperator(operator string) *string {
 	token := t.peek()
+	if token == nil {
+		return nil
+	}
 	if token.role == operatorToken && token.value == operator {
 		t.next()
 		return &(token.value)
diff --git a/spdxexp/parse_test.go b/spdxexp/parse_test.go
index 1d19abe..f0d16bf 100644
--- a/spdxexp/parse_test.go
+++ b/spdxexp/parse_test.go
@@ -41,6 +41,10 @@ func TestParse(t *testing.T) {
 			"MIT", nil},
 
 		{"empty expression", "", nil, "", errors.New("parse error - cannot parse empty string")},
+		{"operator error - nothing after open parenthesis", "(", nil, "", errors.New("open parenthesis does not have a matching close parenthesis")},
+		{"operator error - nested dangling open parenthesis", "((", nil, "", errors.New("open parenthesis does not have a matching close parenthesis")},
+		{"operator error - expression ending in open parenthesis", "MIT OR (", nil, "", errors.New("open parenthesis does not have a matching close parenthesis")},
+		{"document reference without license reference", "DocumentRef-spdx-tool-1.2:", nil, "", errors.New("expected 'LicenseRef-...' after 'DocumentRef-...'")},
 
 		{"invalid license", "NON-EXISTENT-LICENSE", nil, "",
 			errors.New("unknown license 'NON-EXISTENT-LICENSE' at offset 0")},
@@ -1075,6 +1079,7 @@ func TestParseTokens(t *testing.T) {
 			},
 			"{ LEFT: { LEFT: MIT and RIGHT: Apache-1.0+ } or RIGHT: { LEFT: DocumentRef-spdx-tool-1.2:LicenseRef-MIT-Style-2 or RIGHT: GPL-2.0 with Bison-exception-2.2 } }", nil,
 		},
+
 		{"operator error - missing close parenthesis", getMissingEndParenTokens(0),
 			&node{}, "", errors.New("open parenthesis does not have a matching close parenthesis"),
 		},
@@ -1214,6 +1219,7 @@ func TestParseOperator(t *testing.T) {
 		{"looking for + operator", getPlusClauseTokens(1), "+", false, 2},
 		{"looking for OR operator, but got AND", getAndClauseTokens(1), "OR", true, 1},
 		{"looking for OR operator, but got LICENSE", getOrClauseTokens(0), "OR", true, 0},
+		{"looking for operator past end", getAndClauseTokens(3), "OR", true, 3},
 	}
 
 	for _, test := range tests {
diff --git a/spdxexp/satisfies_test.go b/spdxexp/satisfies_test.go
index dc81df7..6955d95 100644
--- a/spdxexp/satisfies_test.go
+++ b/spdxexp/satisfies_test.go
@@ -272,6 +272,15 @@ func TestValidateAndNormalizeLicensesWithOptions_FailComplexExpressions(t *testi
 	}
 }
 
+func TestValidateAndNormalizeLicensesWithOptions_MalformedTrailingTokens(t *testing.T) {
+	licenses := []string{"(", "((", "MIT OR (", "DocumentRef-spdx-tool-1.2:"}
+
+	normalizedLicenses, invalidLicenses := ValidateAndNormalizeLicensesWithOptions(licenses, ValidateLicensesOptions{})
+
+	assert.Empty(t, normalizedLicenses)
+	assert.Equal(t, licenses, invalidLicenses)
+}
+
 func TestValidateAndNormalizeLicensesWithOptions_FailDeprecatedLicenses(t *testing.T) {
 	// eCos-2.0 is a known deprecated SPDX license ID (see TestDeprecatedLicense).
 	deprecatedLicense := "eCos-2.0"