diff --git a/lib/parser.js b/lib/parser.js
index 2ef8bd87e5356ad7132e9b6ba7d49c06da63ab5c..2871049e6a3cffe60eadbd98653cf6280106bde0 100644
--- a/lib/parser.js
+++ b/lib/parser.js
@@ -1638,13 +1638,20 @@ module.exports = class Parser {
 
   selectorParts() {
     var tok
-      , arr = [];
+      , arr = []
+      , parens = 0;
 
     // Selector candidates,
     // stitched together to
     // form a selector.
-    while (tok = this.selectorToken()) {
+    // Commas inside functions belong to this selector, not the group.
+    while (tok = this.selectorToken() || (parens && this.accept(','))) {
       debug.selector('%s', tok);
+      if ('function' == tok.type || '(' == tok.type) {
+        ++parens;
+      } else if (')' == tok.type && parens) {
+        --parens;
+      }
       // Selector component
       switch (tok.type) {
         case '{':
diff --git a/lib/utils.js b/lib/utils.js
index 88e5c3993d464e9b2be1c262d115572c6c9de7de..03516414fd9c5a631f758cb0d87d4f0addad982a 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -426,6 +426,60 @@ exports.uniq = function(arr){
   return ret;
 };
 
+/**
+ * Split a selector list without splitting function arguments or attributes.
+ *
+ * @param {String} str
+ * @return {Array}
+ * @api private
+ */
+
+exports.splitSelectors = function(str){
+  var selectors = []
+    , start = 0
+    , parens = 0
+    , brackets = 0
+    , quote;
+
+  for (var i = 0; i < str.length; ++i) {
+    var c = str[i];
+    if ('\\' == c) {
+      ++i;
+      continue;
+    }
+    if (quote) {
+      if (c == quote) quote = null;
+      continue;
+    }
+    if ('"' == c || "'" == c) {
+      quote = c;
+      continue;
+    }
+    if ('/' == c && '*' == str[i + 1]) {
+      var end = str.indexOf('*/', i + 2);
+      if (-1 == end) break;
+      i = end + 1;
+      continue;
+    }
+    if ('[' == c) {
+      ++brackets;
+    } else if (']' == c) {
+      if (brackets) --brackets;
+    } else if (!brackets) {
+      if ('(' == c) {
+        ++parens;
+      } else if (')' == c) {
+        if (parens) --parens;
+      } else if (',' == c && !parens) {
+        selectors.push(str.slice(start, i));
+        start = i + 1;
+      }
+    }
+  }
+  selectors.push(str.slice(start));
+  return selectors;
+};
+
 /**
  * Compile selector strings in `arr` from the bottom-up
  * to produce the selector combinations. For example
diff --git a/lib/visitor/normalizer.js b/lib/visitor/normalizer.js
index d6d97654f7a4dc9e91db8782a6aba42528283f43..2e614f9feb5c952e37241627e9db6285352765b6 100644
--- a/lib/visitor/normalizer.js
+++ b/lib/visitor/normalizer.js
@@ -237,29 +237,34 @@ module.exports = class Normalizer extends Visitor {
   visitGroup(group) {
     var stack = this.stack
       , map = this.map
-      , parts;
+      , normalized = [];
 
-    // normalize interpolated selectors with comma
-    group.nodes.forEach(function (selector, i) {
-      if (!~selector.val.indexOf(',')) return;
-      if (~selector.val.indexOf('\\,')) {
+    // Normalize interpolated lists without overwriting subsequent selectors.
+    group.nodes.forEach(function (selector) {
+      if (!~selector.val.indexOf(',')) {
+        normalized.push(selector);
+        return;
+      }
+      var parts = utils.splitSelectors(selector.val);
+      if (1 == parts.length) {
         selector.val = selector.val.replace(/\\,/g, ',');
+        normalized.push(selector);
         return;
       }
-      parts = selector.val.split(',');
       var root = '/' == selector.val.charAt(0)
         , part, s;
       for (var k = 0, len = parts.length; k < len; ++k) {
-        part = parts[k].trim();
+        part = parts[k].trim().replace(/\\,/g, ',');
         if (root && k > 0 && !~part.indexOf('&')) {
           part = '/' + part;
         }
         s = new nodes.Selector([new nodes.Literal(part)]);
         s.val = part;
         s.block = group.block;
-        group.nodes[i++] = s;
+        normalized.push(s);
       }
     });
+    group.nodes = normalized;
     stack.push(group.nodes);
 
     var selectors = utils.compileSelectors(stack, true);
diff --git a/test/cases/selectors.pseudo.css b/test/cases/selectors.pseudo.css
index 387e67088e631bc281e700856f85f4b4a154b5ea..629025368d70a53c5d167eaf67879d3be6cfc2ae 100644
--- a/test/cases/selectors.pseudo.css
+++ b/test/cases/selectors.pseudo.css
@@ -94,15 +94,11 @@ label input:blank,
 label span {
   color: #014;
 }
-:is(header,
-main,
-footer) p:hover {
+:is(header, main, footer) p:hover {
   color: #f00;
   cursor: pointer;
 }
-:where(header,
-main,
-footer) p:hover {
+:where(header, main, footer) p:hover {
   color: #f00;
   cursor: pointer;
 }
diff --git a/test/cases/regression.2750.compress.css b/test/cases/regression.2750.compress.css
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.compress.css
@@ -0,0 +1,1 @@
+.scope :is(.a, .b) .item,.scope :where(.c, .d) .item{color:#f00}
diff --git a/test/cases/regression.2750.compress.styl b/test/cases/regression.2750.compress.styl
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.compress.styl
@@ -0,0 +1,6 @@
+// Compression must not move selector fragments across functional arguments.
+
+.scope
+  :is(.a, .b), :where(.c, .d)
+    .item
+      color red
diff --git a/test/cases/regression.2750.css b/test/cases/regression.2750.css
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.css
@@ -0,0 +1,45 @@
+:is(.a, .b) .item {
+  color: #f00;
+}
+.scope :is(.a, .b) .item {
+  color: #f00;
+}
+.menu-item:is(:hover, :focus) {
+  color: #f00;
+}
+.parent:is(.a, .b) .item {
+  color: #f00;
+}
+:where(.a, .b) .item {
+  color: #f00;
+}
+:not(.disabled, :has(> .icon, + .sibling)) .item {
+  color: #f00;
+}
+:has(> .a, + .b) .item {
+  color: #f00;
+}
+:nth-child(2n + 1 of .a, .b) .item {
+  color: #f00;
+}
+.first .item,
+:is(.second, .third) .item,
+.last .item {
+  color: #f00;
+}
+[data-value="a,b"] .item {
+  color: #f00;
+}
+:is([data-value="),x"], :not(.c, .d)) .item {
+  color: #f00;
+}
+:is(.multiline-a,.multiline-b) .item {
+  color: #f00;
+}
+.extend-target:is(.a, .b),
+.extended {
+  color: #f00;
+}
+:is(.escaped-a,.escaped-b) .item {
+  color: #f00;
+}
diff --git a/test/cases/regression.2750.interpolation.css b/test/cases/regression.2750.interpolation.css
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.interpolation.css
@@ -0,0 +1,44 @@
+:is(.a, .b) .item {
+  color: #f00;
+}
+.wrapper :not(.a, :has(> .b, + .c)) .item,
+.wrapper .fallback .item {
+  color: #f00;
+}
+.before .item,
+:is(.a, .b) .item,
+.fallback .item,
+.after .item {
+  color: #f00;
+}
+.attributes [data-value="a,b"] .item,
+.attributes [data-other=",)"] .item {
+  color: #f00;
+}
+.quoted [data-value="a\",b"] .item,
+.quoted .fallback .item {
+  color: #f00;
+}
+:is(.a, .b) .item,
+.fallback .item {
+  color: #f00;
+}
+.legacy :is(.a, .b) .item,
+.legacy .fallback .item {
+  color: #f00;
+}
+.bif:is(.a, .b) .item {
+  color: #f00;
+}
+.single-quoted [data-value='a,b'] .item,
+.single-quoted .fallback .item {
+  color: #f00;
+}
+.escaped-parens .bracket\(x .item,
+.escaped-parens .bracket\)x .item {
+  color: #f00;
+}
+.comments :is(.a, .b /* (, */) .item,
+.comments .fallback .item {
+  color: #f00;
+}
diff --git a/test/cases/regression.2750.interpolation.styl b/test/cases/regression.2750.interpolation.styl
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.interpolation.styl
@@ -0,0 +1,55 @@
+// Preserve functional and attribute commas when expanding interpolated lists.
+
+selector = ':is(.a, .b)'
+{selector}
+  .item
+    color red
+
+.wrapper
+  {':not(.a, :has(> .b, + .c)), .fallback'}
+    .item
+      color red
+
+.before, {':is(.a, .b), .fallback'}, .after
+  .item
+    color red
+
+.attributes
+  {'[data-value="a,b"], [data-other=",)"]'}
+    .item
+      color red
+
+.quoted
+  {'[data-value="a\",b"], .fallback'}
+    .item
+      color red
+
+.root
+  /{':is(.a, .b), .fallback'}
+    .item
+      color red
+
+.legacy
+  {':is(.a\, .b), .fallback'}
+    .item
+      color red
+
+.bif
+  /{selector('&:is(.a, .b)')}
+    .item
+      color red
+
+.single-quoted
+  {"[data-value='a,b'], .fallback"}
+    .item
+      color red
+
+.escaped-parens
+  {'.bracket\(x, .bracket\)x'}
+    .item
+      color red
+
+.comments
+  {':is(.a, .b /* (, */), .fallback'}
+    .item
+      color red
diff --git a/test/cases/regression.2750.styl b/test/cases/regression.2750.styl
new file mode 100644
--- /dev/null
+++ b/test/cases/regression.2750.styl
@@ -0,0 +1,63 @@
+// Keep commas inside functional selectors out of the outer selector list.
+
+:is(.a, .b)
+  .item
+    color red
+
+.scope
+  :is(.a, .b)
+    .item
+      color red
+
+.menu-item:is(:hover, :focus)
+  color red
+
+.parent
+  &:is(.a, .b)
+    .item
+      color red
+
+:where(.a, .b)
+  .item
+    color red
+
+:not(.disabled, :has(> .icon, + .sibling))
+  .item
+    color red
+
+:has(> .a, + .b)
+  .item
+    color red
+
+:nth-child(2n + 1 of .a, .b)
+  .item
+    color red
+
+.first, :is(.second, .third), .last
+  .item
+    color red
+
+[data-value="a,b"]
+  .item
+    color red
+
+:is([data-value="),x"], :not(.c, .d))
+  .item
+    color red
+
+:is(
+  .multiline-a,
+  .multiline-b
+)
+  .item
+    color red
+
+.extend-target:is(.a, .b)
+  color red
+
+.extended
+  @extend .extend-target:is(.a, .b)
+
+:is(.escaped-a\\\, .escaped-b)
+  .item
+    color red