Index: lld/MinGW/Driver.cpp
===================================================================
--- lld/MinGW/Driver.cpp
+++ lld/MinGW/Driver.cpp
@@ -292,7 +292,8 @@
     add("-noseh");
 
   if (args.getLastArgValue(OPT_m) != "thumb2pe" &&
-      args.getLastArgValue(OPT_m) != "arm64pe" && !args.hasArg(OPT_dynamicbase))
+      args.getLastArgValue(OPT_m) != "arm64pe" &&
+      args.hasArg(OPT_no_dynamicbase))
     add("-dynamicbase:no");
 
   if (args.hasFlag(OPT_no_insert_timestamp, OPT_insert_timestamp, false))
Index: lld/MinGW/Options.td
===================================================================
--- lld/MinGW/Options.td
+++ lld/MinGW/Options.td
@@ -32,7 +32,7 @@
     HelpText<"Don't automatically import data symbols from other DLLs without dllimport">;
 def disable_runtime_pseudo_reloc: F<"disable-runtime-pseudo-reloc">,
     HelpText<"Don't do automatic imports that require runtime fixups">;
-def dynamicbase: F<"dynamicbase">, HelpText<"Enable ASLR">;
+defm dynamicbase: B<"dynamicbase", "Enable ASLR", "Disable ASLR">;
 def enable_auto_import: F<"enable-auto-import">,
     HelpText<"Automatically import data symbols from other DLLs where needed">;
 def enable_runtime_pseudo_reloc: F<"enable-runtime-pseudo-reloc">,
Index: lld/test/MinGW/driver.test
===================================================================
--- lld/test/MinGW/driver.test
+++ lld/test/MinGW/driver.test
@@ -136,14 +136,18 @@
 RUN: ld.lld -### -m i386pep foo.o --large-address-aware | FileCheck -check-prefix LARGE-ADDRESS-AWARE %s
 LARGE-ADDRESS-AWARE: -largeaddressaware
 
-RUN: ld.lld -### -m i386pe foo.o | FileCheck -check-prefix DEFAULT-DISABLE-FLAGS %s
-RUN: ld.lld -### -m i386pep foo.o | FileCheck -check-prefix DEFAULT-DISABLE-FLAGS %s
-DEFAULT-DISABLE-FLAGS: -dynamicbase:no
-RUN: ld.lld -### -m i386pe --dynamicbase foo.o | FileCheck -check-prefix NO-DEFAULT-DISABLE-FLAGS %s
-RUN: ld.lld -### -m i386pep -dynamicbase foo.o | FileCheck -check-prefix NO-DEFAULT-DISABLE-FLAGS %s
-RUN: ld.lld -### -m thumb2pe foo.o | FileCheck -check-prefix NO-DEFAULT-DISABLE-FLAGS %s
-RUN: ld.lld -### -m arm64pe foo.o | FileCheck -check-prefix NO-DEFAULT-DISABLE-FLAGS %s
-NO-DEFAULT-DISABLE-FLAGS-NOT: -dynamicbase:no
+RUN: ld.lld -### -m i386pe foo.o --no-dynamicbase | FileCheck -check-prefix DISABLE-DYNAMICBASE %s
+DISABLE-DYNAMICBASE: -dynamicbase:no
+RUN: ld.lld -### -m i386pe --dynamicbase foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m i386pep -dynamicbase foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m i386pe foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m i386pep foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m thumb2pe foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m arm64pe foo.o | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+# On arm, dynamicbase can't be disabled, so --no-dynamicbase is ignored
+RUN: ld.lld -### -m thumb2pe foo.o --no-dynamicbase | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+RUN: ld.lld -### -m arm64pe foo.o --no-dynamicbase | FileCheck -check-prefix NO-DISABLE-DYNAMICBASE %s
+NO-DISABLE-DYNAMICBASE-NOT: -dynamicbase:no
 
 RUN: ld.lld -### -m i386pep foo.o --image-base 0x1230000 | FileCheck -check-prefix IMAGE-BASE %s
 RUN: ld.lld -### -m i386pep foo.o -image-base 0x1230000 | FileCheck -check-prefix IMAGE-BASE %s