diff --git a/.travis.yml b/.travis.yml
index d74b621..4f8956f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ php:
   - 7.1
   - 7.2
   - 7.3
+  - 7.4
   - nightly
 
 matrix:
diff --git a/lib/ResourceOutputStream.php b/lib/ResourceOutputStream.php
index dea2b1a..b8e2d42 100644
--- a/lib/ResourceOutputStream.php
+++ b/lib/ResourceOutputStream.php
@@ -83,10 +83,22 @@ public function __construct($stream, int $chunkSize = null)
                         $written = @\fwrite($stream, $data);
                     }
 
-                    \assert($written !== false, "Trying to write on a previously fclose()'d resource. Do NOT manually fclose() resources the loop still has a reference to.");
+                    \assert(
+                        $written !== false || \PHP_VERSION_ID >= 70400, // PHP 7.4+ returns false on EPIPE.
+                        "Trying to write on a previously fclose()'d resource. Do NOT manually fclose() resources the still referenced in the loop."
+                    );
+
+                    // PHP 7.4.0 and 7.4.1 may return false on EAGAIN.
+                    if ($written === false && \PHP_VERSION_ID >= 70402) {
+                        $message = "Failed to write to stream";
+                        if ($error = \error_get_last()) {
+                            $message .= \sprintf("; %s", $error["message"]);
+                        }
+                        throw new StreamException($message);
+                    }
 
                     // Broken pipes between processes on macOS/FreeBSD do not detect EOF properly.
-                    if ($written === 0) {
+                    if ($written === 0 || $written === false) {
                         if ($emptyWrites++ > self::MAX_CONSECUTIVE_EMPTY_WRITES) {
                             $message = "Failed to write to stream after multiple attempts";
                             if ($error = \error_get_last()) {
@@ -191,7 +203,21 @@ private function send(string $data, bool $end = false): Promise
                 $written = @\fwrite($this->resource, $data);
             }
 
-            \assert($written !== false, "Trying to write on a previously fclose()'d resource. Do NOT manually fclose() resources the loop still has a reference to.");
+            \assert(
+                $written !== false || \PHP_VERSION_ID >= 70400, // PHP 7.4+ returns false on EPIPE.
+                "Trying to write on a previously fclose()'d resource. Do NOT manually fclose() resources the still referenced in the loop."
+            );
+
+            // PHP 7.4.0 and 7.4.1 may return false on EAGAIN.
+            if ($written === false && \PHP_VERSION_ID >= 70402) {
+                $message = "Failed to write to stream";
+                if ($error = \error_get_last()) {
+                    $message .= \sprintf("; %s", $error["message"]);
+                }
+                return new Failure(new StreamException($message));
+            }
+
+            $written = (int) $written; // Cast potential false to 0.
 
             if ($length === $written) {
                 if ($end) {
diff --git a/test/ResourceOutputStreamTest.php b/test/ResourceOutputStreamTest.php
index e186e12..ab1185c 100644
--- a/test/ResourceOutputStreamTest.php
+++ b/test/ResourceOutputStreamTest.php
@@ -44,7 +44,7 @@ public function testBrokenPipe()
         \fclose($b);
 
         $this->expectException(StreamException::class);
-        $this->expectExceptionMessage("Failed to write to stream after multiple attempts; fwrite(): send of 6 bytes failed with errno=32 Broken pipe");
+        $this->expectExceptionMessage("fwrite(): send of 6 bytes failed with errno=32 Broken pipe");
         wait($stream->write("foobar"));
     }
 
@@ -60,7 +60,7 @@ public function testClosedRemoteSocket()
         \fclose($b);
 
         $this->expectException(StreamException::class);
-        $this->expectExceptionMessage("Failed to write to stream after multiple attempts; fwrite(): send of 6 bytes failed with errno=32 Broken pipe");
+        $this->expectExceptionMessage("fwrite(): send of 6 bytes failed with errno=32 Broken pipe");
 
         // The first write still succeeds somehow...
         wait($stream->write("foobar"));