diff --git a/src/connection_string.jl b/src/connection_string.jl
index 47766e0..ddff7fb 100644
--- a/src/connection_string.jl
+++ b/src/connection_string.jl
@@ -157,7 +157,8 @@ function check_ignored_param(key::String, value::String)
     inert = get(SECURITY_SENSITIVE_IGNORED, key, nothing)
     inert === nothing && return
     value in inert && return
-    throw(ArgumentError("connection parameter \"$key=$value\" is not supported by Postgres.jl and cannot be safely ignored"))
+    # never echo the value: for sslpassword it is the client key passphrase
+    throw(ArgumentError("connection parameter \"$key\" is set to a value Postgres.jl does not support and cannot safely ignore"))
 end
 
 # An unrecognized key is almost always a typo, and silently dropping it is
diff --git a/test/runtests.jl b/test/runtests.jl
index e8d63f2..1ba3543 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -649,6 +649,18 @@ include("notification_deadlines.jl")
         @test !occursin("top-secret", plain_shown)
         @test occursin("password=***", shown)
         @test occursin("password=***", plain_shown)
+        # Nor may an error rejecting an option: sslpassword is a key passphrase.
+        for dsn in ("host=h sslpassword=top-secret", "postgresql://u@h/db?sslpassword=top-secret")
+            err = try
+                Postgres.parse_dsn(dsn)
+                nothing
+            catch e
+                e
+            end
+            @test err isa ArgumentError
+            @test occursin("sslpassword", err.msg)
+            @test !occursin("top-secret", sprint(showerror, err))
+        end
 
         # Malformed keyword DSNs must never degrade to a usable partial
         # configuration. In particular, a discarded security option could