diff --git a/Library/Homebrew/dev-cmd/contributions.rb b/Library/Homebrew/dev-cmd/contributions.rb
index 007562fb05..3abc22f96e 100755
--- a/Library/Homebrew/dev-cmd/contributions.rb
+++ b/Library/Homebrew/dev-cmd/contributions.rb
@@ -199,7 +199,7 @@ module Homebrew
 
   sig { params(repo_path: Pathname, person: String, trailer: String, args: Homebrew::CLI::Args).returns(Integer) }
   def git_log_trailers_cmd(repo_path, person, trailer, args)
-    cmd = ["git", "-C", repo_path.to_s, "log", "--oneline"]
+    cmd = ["git", "-C", repo_path, "log", "--oneline"]
     cmd << "--format='%(trailers:key=#{trailer}:)'"
     cmd << "--before=#{args.to}" if args.to
     cmd << "--after=#{args.from}" if args.from
diff --git a/Library/Homebrew/extend/git_repository.rb b/Library/Homebrew/extend/git_repository.rb
index a91ec91704..6e21970e31 100644
--- a/Library/Homebrew/extend/git_repository.rb
+++ b/Library/Homebrew/extend/git_repository.rb
@@ -117,6 +117,6 @@ module GitRepositoryExtension
       raise "Git is unavailable"
     end
 
-    T.unsafe(Utils).popen_read(Utils::Git.git, *args, safe: safe, chdir: self, err: err).chomp.presence
+    Utils.popen_read(Utils::Git.git, *args, safe: safe, chdir: self, err: err).chomp.presence
   end
 end
diff --git a/Library/Homebrew/os/linux/elf.rb b/Library/Homebrew/os/linux/elf.rb
index 4c3c739b31..92212d0d49 100644
--- a/Library/Homebrew/os/linux/elf.rb
+++ b/Library/Homebrew/os/linux/elf.rb
@@ -131,7 +131,7 @@ module ELFShim
       return if needed.empty?
 
       ldd = DevelopmentTools.locate "ldd"
-      ldd_output = Utils.popen_read(T.must(ldd).to_s, path.expand_path.to_s).split("\n")
+      ldd_output = Utils.popen_read(T.must(ldd), path.expand_path.to_s).split("\n")
       return unless $CHILD_STATUS.success?
 
       ldd_paths = ldd_output.map do |line|
diff --git a/Library/Homebrew/os/mac/sdk.rb b/Library/Homebrew/os/mac/sdk.rb
index 04e4c10c88..9068964736 100644
--- a/Library/Homebrew/os/mac/sdk.rb
+++ b/Library/Homebrew/os/mac/sdk.rb
@@ -161,8 +161,7 @@ module OS
           # Xcode.prefix is pretty smart, so let's look inside to find the sdk
           sdk_prefix = "#{Xcode.prefix}/Platforms/MacOSX.platform/Developer/SDKs"
           # Finally query Xcode itself (this is slow, so check it last)
-          sdk_platform_path = Utils.popen_read(DevelopmentTools.locate("xcrun").to_s,
-                                               "--show-sdk-platform-path").chomp
+          sdk_platform_path = Utils.popen_read(T.must(DevelopmentTools.locate("xcrun")), "--show-sdk-platform-path").chomp
           sdk_prefix = File.join(sdk_platform_path, "Developer", "SDKs") unless File.directory? sdk_prefix
 
           sdk_prefix
diff --git a/Library/Homebrew/utils/popen.rb b/Library/Homebrew/utils/popen.rb
index 763672f3d3..6dc2ffa920 100644
--- a/Library/Homebrew/utils/popen.rb
+++ b/Library/Homebrew/utils/popen.rb
@@ -9,11 +9,11 @@ module Utils
 
   sig {
     params(
-      args:    T.any(String, T::Hash[String, String]),
+      args:    T.any(Pathname, String, T::Hash[String, String]),
       safe:    T::Boolean,
-      options: Symbol,
+      options: T.untyped,
       block:   T.nilable(T.proc.params(io: IO).void),
-    ).returns(String)
+    ).returns(T.nilable(String))
   }
   def self.popen_read(*args, safe: false, **options, &block)
     output = popen(args, "rb", options, &block)
@@ -24,10 +24,10 @@ module Utils
 
   sig {
     params(
-      args:    T.any(String, T::Hash[String, String]),
-      options: Symbol,
+      args:    T.any(Pathname, String, T::Hash[String, String]),
+      options: T.untyped,
       block:   T.nilable(T.proc.params(io: IO).void),
-    ).returns(String)
+    ).returns(T.nilable(String))
   }
   def self.safe_popen_read(*args, **options, &block)
     popen_read(*args, safe: true, **options, &block)
@@ -35,11 +35,11 @@ module Utils
 
   sig {
     params(
-      args:    T.any(String, T::Hash[String, String]),
+      args:    T.any(Pathname, String, T::Hash[String, String]),
       safe:    T::Boolean,
-      options: Symbol,
+      options: T.untyped,
       _block:  T.proc.params(io: IO).void,
-    ).returns(String)
+    ).returns(T.nilable(String))
   }
   def self.popen_write(*args, safe: false, **options, &_block)
     output = ""
@@ -66,10 +66,10 @@ module Utils
 
   sig {
     params(
-      args:    T.any(String, T::Hash[String, String]),
-      options: Symbol,
+      args:    T.any(Pathname, String, T::Hash[String, String]),
+      options: T.untyped,
       block:   T.nilable(T.proc.params(io: IO).void),
-    ).returns(String)
+    ).returns(T.nilable(String))
   }
   def self.safe_popen_write(*args, **options, &block)
     popen_write(*args, safe: true, **options, &block)
@@ -77,11 +77,11 @@ module Utils
 
   sig {
     params(
-      args:    T::Array[T.any(String, T::Hash[String, String])],
+      args:    T::Array[T.any(Pathname, String, T::Hash[String, String])],
       mode:    String,
       options: T::Hash[Symbol, T.untyped],
       block:   T.nilable(T.proc.params(io: IO).void),
-    ).returns(String)
+    ).returns(T.nilable(String))
   }
   def self.popen(args, mode, options = {}, &block)
     IO.popen("-", mode) do |pipe|