diff --git a/libc/bionic/err.c b/libc/bionic/err.c
index 535b7e1..84a3d85 100644
--- a/libc/bionic/err.c
+++ b/libc/bionic/err.c
@@ -34,7 +34,7 @@
 #include <stdarg.h>
 #include <errno.h>
 
-extern char *__progname;
+extern const char* __progname;
 
 __noreturn void
 err(int eval, const char *fmt, ...)
diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index 6b4ae2c..71acc45 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -46,7 +46,7 @@
 extern "C" int __system_properties_init(void);
 
 // Not public, but well-known in the BSDs.
-char* __progname;
+const char* __progname;
 
 // Declared in <unistd.h>
 char** environ;
@@ -88,7 +88,7 @@
   environ = args.envp;
   errno = 0;
   __libc_auxv = args.auxv;
-  __progname = args.argv[0] ? args.argv[0] : const_cast<char*>("<unknown>");
+  __progname = args.argv[0] ? args.argv[0] : "<unknown>";
 
   // Get the main thread from TLS and add it to the thread list.
   pthread_internal_t* main_thread = __get_thread();
diff --git a/libc/bionic/malloc_debug_common.cpp b/libc/bionic/malloc_debug_common.cpp
index 248a2db..a05a5ef 100644
--- a/libc/bionic/malloc_debug_common.cpp
+++ b/libc/bionic/malloc_debug_common.cpp
@@ -256,7 +256,7 @@
     dlmalloc, dlfree, dlcalloc, dlrealloc, dlmemalign
 };
 
-extern char* __progname;
+extern const char* __progname;
 
 /* Handle to shared library where actual memory allocation is implemented.
  * This library is loaded and memory allocation calls are redirected there
diff --git a/libc/bionic/pthread_debug.cpp b/libc/bionic/pthread_debug.cpp
index 21eac63..f8f0c59 100644
--- a/libc/bionic/pthread_debug.cpp
+++ b/libc/bionic/pthread_debug.cpp
@@ -116,7 +116,7 @@
 static const char* const kEndBanner =
         "===============================================================";
 
-extern char* __progname;
+extern const char* __progname;
 
 #define STACK_TRACE_DEPTH 16