diff --git a/src/core/parser.js b/src/core/parser.js
index 836dd0ff4..088a26c6e 100644
--- a/src/core/parser.js
+++ b/src/core/parser.js
@@ -897,21 +897,15 @@ class Lexer {
       ch = this.nextChar();
     }
     if (ch < /* '0' = */ 0x30 || ch > /* '9' = */ 0x39) {
+      const msg = `Invalid number: ${String.fromCharCode(ch)} (charCode ${ch})`;
+
       if (isWhiteSpace(ch) || ch === /* EOF = */ -1) {
-        // This is consistent with Adobe Reader (fixes issue9252.pdf).
-        if (divideBy === 10 && sign === 0) {
-          warn("Lexer.getNumber - treating a single decimal point as zero.");
-          return 0;
-        }
-        // This is consistent with Adobe Reader (fixes bug1753983.pdf).
-        if (divideBy === 0 && sign === -1) {
-          warn("Lexer.getNumber - treating a single minus sign as zero.");
-          return 0;
-        }
+        // This is consistent with Adobe Reader (fixes issue9252.pdf,
+        // issue15604.pdf, bug1753983.pdf).
+        info(`Lexer.getNumber - "${msg}".`);
+        return 0;
       }
-      throw new FormatError(
-        `Invalid number: ${String.fromCharCode(ch)} (charCode ${ch})`
-      );
+      throw new FormatError(msg);
     }
 
     sign = sign || 1;
diff --git a/test/pdfs/issue15604.pdf.link b/test/pdfs/issue15604.pdf.link
new file mode 100644
index 000000000..cc76a844d
--- /dev/null
+++ b/test/pdfs/issue15604.pdf.link
@@ -0,0 +1 @@
+https://github.com/mozilla/pdf.js/files/9832017/SP_Page1.pdf
diff --git a/test/test_manifest.json b/test/test_manifest.json
index bad62f408..c782b5efa 100644
--- a/test/test_manifest.json
+++ b/test/test_manifest.json
@@ -288,6 +288,13 @@
        "link": true,
        "type": "eq"
     },
+    {  "id": "issue15604",
+       "file": "pdfs/issue15604.pdf",
+       "md5": "505040e5634434ae97118a4c39bf27e5",
+       "rounds": 1,
+       "link": true,
+       "type": "eq"
+    },
     {  "id": "bug921760",
        "file": "pdfs/bug921760.pdf",
        "md5": "1aa136d786a65b0d7cce7bdb3c58c6c3",
diff --git a/test/unit/parser_spec.js b/test/unit/parser_spec.js
index e346de6da..b286dde86 100644
--- a/test/unit/parser_spec.js
+++ b/test/unit/parser_spec.js
@@ -151,17 +151,17 @@ describe("parser", function () {
         expect(plusLexer.getNumber()).toEqual(205.88);
       });
 
-      it("should treat a single decimal point, or minus sign, as zero", function () {
-        const dotInput = new StringStream(".");
-        const dotLexer = new Lexer(dotInput);
-        expect(dotLexer.getNumber()).toEqual(0);
+      it("should treat a single decimal point, or minus/plus sign, as zero", function () {
+        const validNums = [".", "-", "+", "-.", "+.", "-\r\n.", "+\r\n."];
+        for (const number of validNums) {
+          const validInput = new StringStream(number);
+          const validLexer = new Lexer(validInput);
 
-        const minusInput = new StringStream("-");
-        const minusLexer = new Lexer(minusInput);
-        expect(minusLexer.getNumber()).toEqual(0);
+          expect(validLexer.getNumber()).toEqual(0);
+        }
 
-        const numbers = ["..", "-.", "+.", "-\r\n.", "+\r\n."];
-        for (const number of numbers) {
+        const invalidNums = ["..", ".-", ".+"];
+        for (const number of invalidNums) {
           const invalidInput = new StringStream(number);
           const invalidLexer = new Lexer(invalidInput);