diff --git a/lexer.go b/lexer.go
index 91f93c9..5efbf6b 100644
--- a/lexer.go
+++ b/lexer.go
@@ -68,7 +68,9 @@
 }
 
 func isKeyChar(r rune) bool {
-	return isAlphanumeric(r) || r == '-'
+	// "Keys start with the first non-whitespace character and end with the last
+	// non-whitespace character before the equals sign."
+	return !(isSpace(r) || r == '\n' || r == eof || r == '=')
 }
 
 func isDigit(r rune) bool {
diff --git a/lexer_test.go b/lexer_test.go
index 1d7e37b..6436378 100644
--- a/lexer_test.go
+++ b/lexer_test.go
@@ -113,6 +113,15 @@
 	})
 }
 
+func TestKeyWithSharpAndEqual(t *testing.T) {
+	testFlow(t, "key#name = 5", []token{
+		token{tokenKey, "key#name"},
+		token{tokenEqual, "="},
+		token{tokenInteger, "5"},
+		token{tokenEOF, ""},
+	})
+}
+
 func TestKeyEqualStringEscape(t *testing.T) {
 	testFlow(t, "foo = \"hello\\\"\"", []token{
 		token{tokenKey, "foo"},