diff --git a/src/core/xfa/xhtml.js b/src/core/xfa/xhtml.js
index 3e9847c7beb88..1c1eab989cfd5 100644
--- a/src/core/xfa/xhtml.js
+++ b/src/core/xfa/xhtml.js
@@ -94,7 +94,8 @@ const StyleMapping = new Map([
   [
     "font-size",
     (value, original) => {
-      value = original.fontSize = getMeasurement(value);
+      // The font size must be positive.
+      value = original.fontSize = Math.abs(getMeasurement(value));
       return measureToString(0.99 * value);
     },
   ],
diff --git a/test/unit/xfa_tohtml_spec.js b/test/unit/xfa_tohtml_spec.js
index e4284963926b0..615ba3c123d75 100644
--- a/test/unit/xfa_tohtml_spec.js
+++ b/test/unit/xfa_tohtml_spec.js
@@ -642,4 +642,45 @@ describe("XFAFactory", function () {
     expect(a.attributes.href).toEqual("https://github.com/allizom/pdf.js");
     expect(a.attributes.newWindow).toEqual(false);
   });
+
+  it("should take the absolute value of the font size", async () => {
+    const xml = `
+<?xml version="1.0"?>
+<xdp:xdp xmlns:xdp="http://ns.adobe.com/xdp/">
+  <template xmlns="http://www.xfa.org/schema/xfa-template/3.3">
+    <subform name="root" mergeMode="matchTemplate">
+      <pageSet>
+        <pageArea>
+          <contentArea x="0pt" w="456pt" h="789pt"/>
+          <draw y="1pt" w="11pt" h="22pt" x="2pt">
+            <value>
+              <text>
+                <body xmlns="http://www.w3.org/1999/xhtml">
+                  <p style="foo: bar; text-indent:0.5in; line-height:11px;font-size: -14.0pt; bar:foo;tab-stop: left 0.5in;">
+                    The first line of this paragraph is indented a half-inch.<br/>
+                    Successive lines are not indented.<br/>
+                    This is the last line of the paragraph.<br/>
+                  </p>
+                </body>
+              </text>
+            </value>
+          </draw>
+        </pageArea>
+      </pageSet>
+    </subform>
+  </template>
+  <xfa:datasets xmlns:xfa="http://www.xfa.org/schema/xfa-data/1.0/">
+    <xfa:data>
+    </xfa:data>
+  </xfa:datasets>
+</xdp:xdp>
+    `;
+    const factory = new XFAFactory({ "xdp:xdp": xml });
+
+    expect(await factory.getNumPages()).toEqual(1);
+
+    const pages = await factory.getPages();
+    const p = searchHtmlNode(pages, "name", "p");
+    expect(p.attributes.style.fontSize).toEqual("13.86px");
+  });
 });
