diff --git a/dlls/mshtml/omnavigator.c b/dlls/mshtml/omnavigator.c
index a6c66d18a20..e0b8f73438e 100644
--- a/dlls/mshtml/omnavigator.c
+++ b/dlls/mshtml/omnavigator.c
@@ -1008,6 +1008,7 @@ static HRESULT WINAPI OmNavigator_get_appVersion(IOmNavigator *iface, BSTR *p)
     char user_agent[512];
     DWORD size;
     HRESULT hres;
+    const unsigned skip_prefix = 8; /* strlen("Mozilla/") */
 
     TRACE("(%p)->(%p)\n", This, p);
 
@@ -1016,17 +1017,17 @@ static HRESULT WINAPI OmNavigator_get_appVersion(IOmNavigator *iface, BSTR *p)
     if(FAILED(hres))
         return hres;
 
-    if(strncmp(user_agent, "Mozilla/", 8)) {
-        FIXME("Unsupported user agent\n");
-        return E_FAIL;
+    if(size <= skip_prefix) {
+        *p = NULL;
+        return S_OK;
     }
 
-    size = MultiByteToWideChar(CP_ACP, 0, user_agent+8, -1, NULL, 0);
+    size = MultiByteToWideChar(CP_ACP, 0, user_agent + skip_prefix, -1, NULL, 0);
     *p = SysAllocStringLen(NULL, size-1);
     if(!*p)
         return E_OUTOFMEMORY;
 
-    MultiByteToWideChar(CP_ACP, 0, user_agent+8, -1, *p, size);
+    MultiByteToWideChar(CP_ACP, 0, user_agent + skip_prefix, -1, *p, size);
     return S_OK;
 }
 
diff --git a/dlls/mshtml/tests/dom.c b/dlls/mshtml/tests/dom.c
index 69b62069f3e..8f822995858 100644
--- a/dlls/mshtml/tests/dom.c
+++ b/dlls/mshtml/tests/dom.c
@@ -6228,6 +6228,7 @@ static void test_navigator(IHTMLDocument2 *doc)
     HRESULT hres;
 
     static const WCHAR v40[] = {'4','.','0'};
+    static char ua[] = "1234567890xxxABC";
 
     hres = IHTMLDocument2_get_parentWindow(doc, &window);
     ok(hres == S_OK, "parentWidnow failed: %08x\n", hres);
@@ -6336,6 +6337,17 @@ static void test_navigator(IHTMLDocument2 *doc)
         skip("nonstandard user agent\n");
     }
 
+    hres = UrlMkSetSessionOption(URLMON_OPTION_USERAGENT, ua, sizeof(ua), 0);
+    ok(hres == S_OK, "UrlMkSetSessionOption failed: %08x\n", hres);
+
+    hres = IOmNavigator_get_appVersion(navigator, &bstr);
+    ok(hres == S_OK, "get_appVersion failed: %08x\n", hres);
+    ok(!strcmp_wa(bstr, ua+8), "appVersion returned %s, expected \"%s\"\n", wine_dbgstr_w(bstr), buf+8);
+    SysFreeString(bstr);
+
+    hres = UrlMkSetSessionOption(URLMON_OPTION_USERAGENT, buf, strlen(buf), 0);
+    ok(hres == S_OK, "UrlMkSetSessionOption failed: %08x\n", hres);
+
     bstr = NULL;
     hres = IOmNavigator_get_appMinorVersion(navigator, &bstr);
     ok(hres == S_OK, "get_appMonorVersion failed: %08x\n", hres);