diff --git a/pkgs/by-name/lo/local-ai/package.nix b/pkgs/by-name/lo/local-ai/package.nix
index 498cc96a454b..56b2ba80bf4a 100644
--- a/pkgs/by-name/lo/local-ai/package.nix
+++ b/pkgs/by-name/lo/local-ai/package.nix
@@ -488,7 +488,7 @@ let
         ''${enableParallelBuilding:+-j''${NIX_BUILD_CORES}}
         SHELL=$SHELL
       )
-      _accumFlagsArray makeFlags makeFlagsArray buildFlags buildFlagsArray
+      concatTo flagsArray makeFlags makeFlagsArray buildFlags buildFlagsArray
       echoCmd 'build flags' "''${flagsArray[@]}"
       make build "''${flagsArray[@]}"
       unset flagsArray
diff --git a/pkgs/by-name/me/meson/setup-hook.sh b/pkgs/by-name/me/meson/setup-hook.sh
index 826664545227..7ded366d4032 100644
--- a/pkgs/by-name/me/meson/setup-hook.sh
+++ b/pkgs/by-name/me/meson/setup-hook.sh
@@ -25,7 +25,7 @@ mesonConfigurePhase() {
         "--buildtype=${mesonBuildType:-plain}"
     )
 
-    _accumFlagsArray mesonFlags mesonFlagsArray
+    concatTo flagsArray mesonFlags mesonFlagsArray
 
     echoCmd 'mesonConfigurePhase flags' "${flagsArray[@]}"
 
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index 8255f3aaafb7..810d64ba7a21 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -334,23 +334,24 @@ appendToVar() {
     fi
 }
 
-# Accumulate into `flagsArray` the flags from the named variables.
+# Accumulate flags from the named variables $2+ into the indexed array $1.
 #
 # Arrays are simply concatenated, strings are split on whitespace.
-_accumFlagsArray() {
+concatTo() {
+    local -n targetref="$1"; shift
     local name type
     for name in "$@"; do
         if type=$(declare -p "$name" 2> /dev/null); then
             local -n nameref="$name"
             case "${type#* }" in
                 -A*)
-                    echo "_accumFlagsArray(): ERROR: trying to use _accumFlagsArray on an associative array." >&2
+                    echo "concatTo(): ERROR: trying to use concatTo on an associative array." >&2
                     return 1 ;;
                 -a*)
-                    flagsArray+=( "${nameref[@]}" ) ;;
+                    targetref+=( "${nameref[@]}" ) ;;
                 *)
                     # shellcheck disable=SC2206
-                    flagsArray+=( ${nameref-} ) ;;
+                    targetref+=( ${nameref-} ) ;;
             esac
         fi
     done
@@ -1167,12 +1168,7 @@ unpackPhase() {
     fi
 
     local -a srcsArray
-    if [ -n "$__structuredAttrs" ]; then
-        srcsArray=( "${srcs[@]}" )
-    else
-        # shellcheck disable=SC2206
-        srcsArray=( $srcs )
-    fi
+    concatTo srcsArray srcs
 
     # To determine the source directory created by unpacking the
     # source archives, we record the contents of the current
@@ -1237,13 +1233,7 @@ patchPhase() {
     runHook prePatch
 
     local -a patchesArray
-    if [ -n "$__structuredAttrs" ]; then
-        # shellcheck disable=SC2206
-        patchesArray=( ${patches:+"${patches[@]}"} )
-    else
-        # shellcheck disable=SC2206
-        patchesArray=( ${patches:-} )
-    fi
+    concatTo patchesArray patches
 
     for i in "${patchesArray[@]}"; do
         echo "applying patch $i"
@@ -1355,7 +1345,7 @@ configurePhase() {
 
     if [ -n "$configureScript" ]; then
         local -a flagsArray
-        _accumFlagsArray configureFlags configureFlagsArray
+        concatTo flagsArray configureFlags configureFlagsArray
 
         echoCmd 'configure flags' "${flagsArray[@]}"
         # shellcheck disable=SC2086
@@ -1382,7 +1372,7 @@ buildPhase() {
             ${enableParallelBuilding:+-j${NIX_BUILD_CORES}}
             SHELL="$SHELL"
         )
-        _accumFlagsArray makeFlags makeFlagsArray buildFlags buildFlagsArray
+        concatTo flagsArray makeFlags makeFlagsArray buildFlags buildFlagsArray
 
         echoCmd 'build flags' "${flagsArray[@]}"
         make ${makefile:+-f $makefile} "${flagsArray[@]}"
@@ -1421,14 +1411,14 @@ checkPhase() {
             SHELL="$SHELL"
         )
 
-        _accumFlagsArray makeFlags makeFlagsArray
+        concatTo flagsArray makeFlags makeFlagsArray
         if [ -n "$__structuredAttrs" ]; then
             flagsArray+=( "${checkFlags[@]:-VERBOSE=y}" )
         else
             # shellcheck disable=SC2206
             flagsArray+=( ${checkFlags:-VERBOSE=y} )
         fi
-        _accumFlagsArray checkFlagsArray
+        concatTo flagsArray checkFlagsArray
         # shellcheck disable=SC2206
         flagsArray+=( ${checkTarget} )
 
@@ -1463,7 +1453,7 @@ installPhase() {
         ${enableParallelInstalling:+-j${NIX_BUILD_CORES}}
         SHELL="$SHELL"
     )
-    _accumFlagsArray makeFlags makeFlagsArray installFlags installFlagsArray
+    concatTo flagsArray makeFlags makeFlagsArray installFlags installFlagsArray
     if [ -n "$__structuredAttrs" ]; then
         flagsArray+=( "${installTargets[@]:-install}" )
     else
@@ -1552,7 +1542,7 @@ installCheckPhase() {
             SHELL="$SHELL"
         )
 
-        _accumFlagsArray makeFlags makeFlagsArray \
+        concatTo flagsArray makeFlags makeFlagsArray \
           installCheckFlags installCheckFlagsArray
         # shellcheck disable=SC2206
         flagsArray+=( ${installCheckTarget:-installcheck} )
@@ -1570,7 +1560,7 @@ distPhase() {
     runHook preDist
 
     local flagsArray=()
-    _accumFlagsArray distFlags distFlagsArray
+    concatTo flagsArray distFlags distFlagsArray
     # shellcheck disable=SC2206
     flagsArray+=( ${distTarget:-dist} )
 
diff --git a/pkgs/test/stdenv/default.nix b/pkgs/test/stdenv/default.nix
index 72310b74061f..996087ae32be 100644
--- a/pkgs/test/stdenv/default.nix
+++ b/pkgs/test/stdenv/default.nix
@@ -96,6 +96,41 @@ let
         '';
       } // extraAttrs);
 
+  testConcatTo = { name, stdenv', extraAttrs ? { } }:
+    stdenv'.mkDerivation
+      ({
+        inherit name;
+
+        string = "a b";
+        list = ["c" "d"];
+
+        passAsFile = [ "buildCommand" ] ++ lib.optionals (extraAttrs ? extraTest) [ "extraTest" ];
+        buildCommand = ''
+          declare -A associativeArray=(["X"]="Y")
+          [[ $(concatTo nowhere associativeArray 2>&1) =~ "trying to use" ]] || (echo "concatTo did not throw concatenating associativeArray" && false)
+
+          declare -a flagsArray
+          concatTo flagsArray string list
+          declare -p flagsArray
+          [[ "''${flagsArray[0]}" == "a" ]] || (echo "'\$flagsArray[0]' was not 'a'" && false)
+          [[ "''${flagsArray[1]}" == "b" ]] || (echo "'\$flagsArray[1]' was not 'b'" && false)
+          [[ "''${flagsArray[2]}" == "c" ]] || (echo "'\$flagsArray[2]' was not 'c'" && false)
+          [[ "''${flagsArray[3]}" == "d" ]] || (echo "'\$flagsArray[3]' was not 'd'" && false)
+
+          # test concatenating to unset variable
+          concatTo nonExistant string list
+          declare -p nonExistant
+          [[ "''${nonExistant[0]}" == "a" ]] || (echo "'\$nonExistant[0]' was not 'a'" && false)
+          [[ "''${nonExistant[1]}" == "b" ]] || (echo "'\$nonExistant[1]' was not 'b'" && false)
+          [[ "''${nonExistant[2]}" == "c" ]] || (echo "'\$nonExistant[2]' was not 'c'" && false)
+          [[ "''${nonExistant[3]}" == "d" ]] || (echo "'\$nonExistant[3]' was not 'd'" && false)
+
+          eval "$extraTest"
+
+          touch $out
+        '';
+      } // extraAttrs);
+
 in
 
 {
@@ -196,6 +231,11 @@ in
     stdenv' = bootStdenv;
   };
 
+  test-concat-to = testConcatTo {
+    name = "test-concat-to";
+    stdenv' = bootStdenv;
+  };
+
   test-structured-env-attrset = testEnvAttrset {
     name = "test-structured-env-attrset";
     stdenv' = bootStdenv;
@@ -255,6 +295,24 @@ in
       };
     };
 
+    test-concat-to = testConcatTo {
+      name = "test-concat-to-structuredAttrsByDefault";
+      stdenv' = bootStdenvStructuredAttrsByDefault;
+      extraAttrs = {
+        # test that whitespace is kept in the bash array for structuredAttrs
+        listWithSpaces = [ "c c" "d d" ];
+        extraTest = ''
+          declare -a flagsWithSpaces
+          concatTo flagsWithSpaces string listWithSpaces
+          declare -p flagsWithSpaces
+          [[ "''${flagsWithSpaces[0]}" == "a" ]] || (echo "'\$flagsWithSpaces[0]' was not 'a'" && false)
+          [[ "''${flagsWithSpaces[1]}" == "b" ]] || (echo "'\$flagsWithSpaces[1]' was not 'b'" && false)
+          [[ "''${flagsWithSpaces[2]}" == "c c" ]] || (echo "'\$flagsWithSpaces[2]' was not 'c c'" && false)
+          [[ "''${flagsWithSpaces[3]}" == "d d" ]] || (echo "'\$flagsWithSpaces[3]' was not 'd d'" && false)
+        '';
+      };
+    };
+
     test-golden-example-structuredAttrs =
       let
         goldenSh = earlyPkgs.writeText "goldenSh" ''