diff --git a/Cargo.toml b/Cargo.toml
index de61fffe..822bb24e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,7 +22,7 @@ inventory = { version = "0.1.4", optional = true }
 libc = "0.2.62"
 parking_lot = "0.11.0"
 num-bigint = { version = "0.4", optional = true }
-num-complex = { version = "0.3", optional = true }
+num-complex = { version = "0.4", optional = true }
 # must stay at 0.1.x for Rust 1.41 compatibility
 paste = { version = "0.1.18", optional = true }
 pyo3-macros = { path = "pyo3-macros", version = "=0.13.2", optional = true }