diff --git a/dlls/mshtml/htmlstyle.c b/dlls/mshtml/htmlstyle.c
index 6f592502d8c..a467d2e4892 100644
--- a/dlls/mshtml/htmlstyle.c
+++ b/dlls/mshtml/htmlstyle.c
@@ -156,6 +156,8 @@ static const WCHAR min_heightW[] =
     {'m','i','n','-','h','e','i','g','h','t',0};
 static const WCHAR min_widthW[] =
     {'m','i','n','-','w','i','d','t','h',0};
+static const WCHAR opacityW[] =
+    {'o','p','a','c','i','t','y',0};
 static const WCHAR outlineW[] =
     {'o','u','t','l','i','n','e',0};
 static const WCHAR overflowW[] =
@@ -393,6 +395,7 @@ static const style_tbl_entry_t style_tbl[] = {
     {max_widthW,              DISPID_IHTMLSTYLE5_MAXWIDTH,             ATTR_FIX_PX},
     {min_heightW,             DISPID_IHTMLSTYLE4_MINHEIGHT},
     {min_widthW,              DISPID_IHTMLSTYLE5_MINWIDTH,             ATTR_FIX_PX},
+    {opacityW,                DISPID_UNKNOWN},
     {outlineW,                DISPID_IHTMLSTYLE6_OUTLINE,              ATTR_NO_NULL},
     {overflowW,               DISPID_IHTMLSTYLE_OVERFLOW,              0, overflow_values},
     {overflow_xW,             DISPID_IHTMLSTYLE2_OVERFLOWX},
@@ -6796,15 +6799,15 @@ static HRESULT WINAPI HTMLCSSStyleDeclaration_get_fontStretch(IHTMLCSSStyleDecla
 static HRESULT WINAPI HTMLCSSStyleDeclaration_put_opacity(IHTMLCSSStyleDeclaration *iface, VARIANT v)
 {
     HTMLStyle *This = impl_from_IHTMLCSSStyleDeclaration(iface);
-    FIXME("(%p)->(%s)\n", This, debugstr_variant(&v));
-    return E_NOTIMPL;
+    TRACE("(%p)->(%s)\n", This, debugstr_variant(&v));
+    return set_style_property_var(This, STYLEID_OPACITY, &v);
 }
 
 static HRESULT WINAPI HTMLCSSStyleDeclaration_get_opacity(IHTMLCSSStyleDeclaration *iface, VARIANT *p)
 {
     HTMLStyle *This = impl_from_IHTMLCSSStyleDeclaration(iface);
-    FIXME("(%p)->(%p)\n", This, p);
-    return E_NOTIMPL;
+    TRACE("(%p)->(%p)\n", This, p);
+    return get_style_property_var(This, STYLEID_OPACITY, p);
 }
 
 static HRESULT WINAPI HTMLCSSStyleDeclaration_put_clipPath(IHTMLCSSStyleDeclaration *iface, BSTR v)
diff --git a/dlls/mshtml/htmlstyle.h b/dlls/mshtml/htmlstyle.h
index 1a83d4f8e9f..2e5cb27e1dc 100644
--- a/dlls/mshtml/htmlstyle.h
+++ b/dlls/mshtml/htmlstyle.h
@@ -94,6 +94,7 @@ typedef enum {
     STYLEID_MAX_WIDTH,
     STYLEID_MIN_HEIGHT,
     STYLEID_MIN_WIDTH,
+    STYLEID_OPACITY,
     STYLEID_OUTLINE,
     STYLEID_OVERFLOW,
     STYLEID_OVERFLOW_X,
diff --git a/dlls/mshtml/tests/style.c b/dlls/mshtml/tests/style.c
index 309ca4029a5..72f36900e38 100644
--- a/dlls/mshtml/tests/style.c
+++ b/dlls/mshtml/tests/style.c
@@ -738,6 +738,7 @@ static void test_style6(IHTMLStyle6 *style)
 
 static void test_css_style_declaration(IHTMLCSSStyleDeclaration *css_style)
 {
+    VARIANT v;
     BSTR str;
     HRESULT hres;
 
@@ -754,6 +755,31 @@ static void test_css_style_declaration(IHTMLCSSStyleDeclaration *css_style)
     ok(hres == S_OK, "get_backgroundClip failed: %08x\n", hres);
     ok(!strcmp_wa(str, "border-box"), "backgroundClip = %s\n", wine_dbgstr_w(str));
     SysFreeString(str);
+
+    hres = IHTMLCSSStyleDeclaration_get_opacity(css_style, &v);
+    ok(hres == S_OK, "get_opacity failed: %08x\n", hres);
+    test_var_bstr(&v, NULL);
+
+    V_VT(&v) = VT_I4;
+    V_I4(&v) = 0;
+    hres = IHTMLCSSStyleDeclaration_put_opacity(css_style, v);
+    ok(hres == S_OK, "put_opacity failed: %08x\n", hres);
+
+    hres = IHTMLCSSStyleDeclaration_get_opacity(css_style, &v);
+    ok(hres == S_OK, "get_opacity failed: %08x\n", hres);
+    test_var_bstr(&v, "0");
+    VariantClear(&v);
+
+    V_VT(&v) = VT_BSTR;
+    V_BSTR(&v) = a2bstr("1");
+    hres = IHTMLCSSStyleDeclaration_put_opacity(css_style, v);
+    ok(hres == S_OK, "put_opacity failed: %08x\n", hres);
+    VariantClear(&v);
+
+    hres = IHTMLCSSStyleDeclaration_get_opacity(css_style, &v);
+    ok(hres == S_OK, "get_opacity failed: %08x\n", hres);
+    test_var_bstr(&v, "1");
+    VariantClear(&v);
 }
 
 static void test_body_style(IHTMLStyle *style)
@@ -1790,6 +1816,14 @@ static void test_body_style(IHTMLStyle *style)
     ok(hres == S_OK, "put_filter failed: %08x\n", hres);
     SysFreeString(str);
 
+    hres = IHTMLStyle_put_filter(style, NULL);
+    ok(hres == S_OK, "put_filter failed: %08x\n", hres);
+
+    str = (void*)0xdeadbeef;
+    hres = IHTMLStyle_get_filter(style, &str);
+    ok(hres == S_OK, "get_filter failed: %08x\n", hres);
+    ok(!str, "filter != NULL\n");
+
     V_VT(&v) = VT_EMPTY;
     hres = IHTMLStyle_get_zIndex(style, &v);
     ok(hres == S_OK, "get_zIndex failed: %08x\n", hres);