diff --git a/conda/environments/all_cuda-118_arch-x86_64.yaml b/conda/environments/all_cuda-118_arch-x86_64.yaml
index e64b94bad6..bf73b938a5 100644
--- a/conda/environments/all_cuda-118_arch-x86_64.yaml
+++ b/conda/environments/all_cuda-118_arch-x86_64.yaml
@@ -71,9 +71,9 @@ dependencies:
 - scipy>=1.8.0
 - seaborn
 - spdlog>=1.14.1,<1.15
+- sphinx
 - sphinx-copybutton
 - sphinx-markdown-tables
-- sphinx<6
 - statsmodels
 - sysroot_linux-64==2.17
 - treelite==4.3.0
diff --git a/conda/environments/all_cuda-125_arch-x86_64.yaml b/conda/environments/all_cuda-125_arch-x86_64.yaml
index 8c4ae0f538..72539f2d18 100644
--- a/conda/environments/all_cuda-125_arch-x86_64.yaml
+++ b/conda/environments/all_cuda-125_arch-x86_64.yaml
@@ -67,9 +67,9 @@ dependencies:
 - scipy>=1.8.0
 - seaborn
 - spdlog>=1.14.1,<1.15
+- sphinx
 - sphinx-copybutton
 - sphinx-markdown-tables
-- sphinx<6
 - statsmodels
 - sysroot_linux-64==2.17
 - treelite==4.3.0
diff --git a/dependencies.yaml b/dependencies.yaml
index 2cd00f78fb..773afce021 100644
--- a/dependencies.yaml
+++ b/dependencies.yaml
@@ -464,7 +464,7 @@ dependencies:
           - pydata-sphinx-theme!=0.14.2
           - recommonmark
           - &scikit_learn scikit-learn==1.5.*
-          - sphinx<6
+          - sphinx
           - sphinx-copybutton
           - sphinx-markdown-tables
       - output_types: conda