diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 60e1b465ba96d..dbd6325a46cc9 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -1401,7 +1401,7 @@ impl Options {
         match self.unstable_opts.share_generics {
             Some(setting) => setting,
             None => match self.optimize {
-                OptLevel::No | OptLevel::Less | OptLevel::Size | OptLevel::SizeMin => true,
+                OptLevel::No | OptLevel::Less | OptLevel::Size | OptLevel::SizeMin => false,
                 OptLevel::More | OptLevel::Aggressive => false,
             },
         }