diff --git a/Cargo.lock b/Cargo.lock
index 4127625b..ca5ee0c1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1837,9 +1837,9 @@ dependencies = [
 
 [[package]]
 name = "z3"
-version = "0.20.2"
+version = "0.21.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "80c4de445f5c9e3013703a6b8a40c80b4a64c925f0a19e7d0a23a7a9b70e854d"
+checksum = "08975512fd325de2a15eede8ed293b2189c745e0770886fae2b30ae229c5b886"
 dependencies = [
  "log",
  "z3-sys",
@@ -1847,9 +1847,9 @@ dependencies = [
 
 [[package]]
 name = "z3-sys"
-version = "0.11.0"
+version = "0.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c18b0a91a13522d21b3414847667de2b2056a721a3edcb5b6ee6858352d58db4"
+checksum = "96975839f50a909f6ec19671e5c06d7f0d6fc67287a120e1b010c5f8d91944d6"
 dependencies = [
  "pkg-config",
 ]
diff --git a/crates/synth-verify/Cargo.toml b/crates/synth-verify/Cargo.toml
index 20627f43..1356ebd0 100644
--- a/crates/synth-verify/Cargo.toml
+++ b/crates/synth-verify/Cargo.toml
@@ -48,7 +48,7 @@ ordeal = "=0.19.0"
 # Default features only (NO `static-link-z3`/`bundled`): z3-sys links the
 # system libz3 (`libz3-dev`) instead of compiling z3 from source or downloading
 # a prebuilt — kills the flaky `build.rs` GitHub download (HTTP 403/502, #553).
-z3 = { version = "0.20", optional = true }
+z3 = { version = "0.21", optional = true }
 
 # Error handling
 anyhow.workspace = true