diff --git a/ChangeLog.d/_GNU_SOURCE-redefined.txt b/ChangeLog.d/_GNU_SOURCE-redefined.txt
new file mode 100644
index 0000000..59c8a15
--- /dev/null
+++ b/ChangeLog.d/_GNU_SOURCE-redefined.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix the build when the macro _GNU_SOURCE is defined to a non-empty value.
+     Fix #3432.
diff --git a/library/entropy_poll.c b/library/entropy_poll.c
index 4ad878e..d7062ea 100644
--- a/library/entropy_poll.c
+++ b/library/entropy_poll.c
@@ -44,7 +44,7 @@
  *  **********
  */
 
-#if defined(__linux__)
+#if defined(__linux__) && !defined(_GNU_SOURCE)
 /* Ensure that syscall() is available even when compiling with -std=c99 */
 #define _GNU_SOURCE
 #endif