diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index fb6e204b5d1..7df4e4a2b44 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -896,11 +896,13 @@ substituteAllStream() {
 # Substitute all environment variables that start with a lowercase character and
 # are valid Bash names.
 substituteAll() {
+    echo HERE
     local input="$1"
     local output="$2"
 
     local -a args=()
     _allFlags
+    declare -p args
 
     substitute "$input" "$output" "${args[@]}"
 }

test-cc-wrapper-substitutions-structuredAttrsByDefault> HERE
test-cc-wrapper-substitutions-structuredAttrsByDefault> declare -a args=([0]="--subst-var" [1]="named_cc" [2]="--subst-var" [3]="use_response_file_by_default" [4]="--subst-var" [5]="out" [6]="--subst-var" [7]="prog" [8]="--subst-var" [9]="named_cxx")

test-cc-wrapper-substitutions> HERE
test-cc-wrapper-substitutions> declare -a args=([0]="--subst-var" [1]="expandResponseParams" [2]="--subst-var" [3]="cc" [4]="--subst-var" [5]="depsTargetTargetPropagated" [6]="--subst-var" [7]="cmakeFlags" [8]="--
subst-var" [9]="coreutils_bin" [10]="--subst-var" [11]="strictDeps" [12]="--subst-var" [13]="bintools" [14]="--subst-var" [15]="version" [16]="--subst-var" [17]="doInstallCheck" [18]="--subst-var" [19]="depsBuildB
uild" [20]="--subst-var" [21]="out" [22]="--subst-var" [23]="enableParallelChecking" [24]="--subst-var" [25]="dontConfigure" [26]="--subst-var" [27]="darwinMinVersionVariable" [28]="--subst-var" [29]="wrapperName"
 [30]="--subst-var" [31]="enableParallelBuilding" [32]="--subst-var" [33]="libc_bin" [34]="--subst-var" [35]="depsBuildTarget" [36]="--subst-var" [37]="nativeBuildInputs" [38]="--subst-var" [39]="dontBuild" [40]="
--subst-var" [41]="darwinPlatformForCC" [42]="--subst-var" [43]="outputs" [44]="--subst-var" [45]="stdenv" [46]="--subst-var" [47]="wrapper" [48]="--subst-var" [49]="libc_lib" [50]="--subst-var" [51]="depsHostHost
Propagated" [52]="--subst-var" [53]="buildInputs" [54]="--subst-var" [55]="shell" [56]="--subst-var" [57]="postFixup" [58]="--subst-var" [59]="depsBuildBuildPropagated" [60]="--subst-var" [61]="installPhase" [62]=
"--subst-var" [63]="darwinMinVersion" [64]="--subst-var" [65]="prog" [66]="--subst-var" [67]="system" [68]="--subst-var" [69]="preferLocalBuild" [70]="--subst-var" [71]="gnugrep_bin" [72]="--subst-var" [73]="meson
Flags" [74]="--subst-var" [75]="libc_dev" [76]="--subst-var" [77]="depsBuildTargetPropagated" [78]="--subst-var" [79]="configureFlags" [80]="--subst-var" [81]="propagatedNativeBuildInputs" [82]="--subst-var" [83]=
"propagatedBuildInputs" [84]="--subst-var" [85]="depsTargetTarget" [86]="--subst-var" [87]="named_cxx" [88]="--subst-var" [89]="depsHostHost" [90]="--subst-var" [91]="builder" [92]="--subst-var" [93]="suffixSalt"
[94]="--subst-var" [95]="doCheck" [96]="--subst-var" [97]="patches" [98]="--subst-var" [99]="named_cc" [100]="--subst-var" [101]="pname" [102]="--subst-var" [103]="name" [104]="--subst-var" [105]="setupHooks" [106
]="--subst-var" [107]="unpackPhase" [108]="--subst-var" [109]="use_response_file_by_default")

diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index fb6e204b5d1..934af6001ce 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -878,6 +878,8 @@ substituteInPlace() {
 }
 
 _allFlags() {
+    echo HERE1 >&2
+    env >&2
     for varName in $(awk 'BEGIN { for (v in ENVIRON) if (v ~ /^[a-z][a-zA-Z0-9_]*$/) print v }'); do
         if (( "${NIX_DEBUG:-0}" >= 1 )); then
             printf "@%s@ -> %q\n" "${varName}" "${!varName}"
@@ -896,11 +898,13 @@ substituteAllStream() {
 # Substitute all environment variables that start with a lowercase character and
 # are valid Bash names.
 substituteAll() {
+    echo HERE
     local input="$1"
     local output="$2"
 
     local -a args=()
     _allFlags
+    declare -p args
 
     substitute "$input" "$output" "${args[@]}"
 }

env doesn't contain the variables

diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index fb6e204b5d1..934af6001ce 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -878,6 +878,8 @@ substituteInPlace() {
 }
 
 _allFlags() {
+    echo HERE1 >&2
+    env >&2
     for varName in $(awk 'BEGIN { for (v in ENVIRON) if (v ~ /^[a-z][a-zA-Z0-9_]*$/) print v }'); do
         if (( "${NIX_DEBUG:-0}" >= 1 )); then
             printf "@%s@ -> %q\n" "${varName}" "${!varName}"
@@ -896,11 +898,13 @@ substituteAllStream() {
 # Substitute all environment variables that start with a lowercase character and
 # are valid Bash names.
 substituteAll() {
+    echo HERE
     local input="$1"
     local output="$2"
 
     local -a args=()
     _allFlags
+    declare -p args
 
     substitute "$input" "$output" "${args[@]}"
 }

the output of env doesn't contain the variables